Update copyright years.

Makefile.am

 # Makefile.am -- Backtrace Makefile.
-# Copyright (C) 2012-2020 Free Software Foundation, Inc.
+# Copyright (C) 2012-2021 Free Software Foundation, Inc.
 
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are

alloc.c

 /* alloc.c -- Memory allocation without mmap.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

allocfail.c

 /* allocfail.c -- Test for libbacktrace library
-   Copyright (C) 2018-2020 Free Software Foundation, Inc.
+   Copyright (C) 2018-2021 Free Software Foundation, Inc.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are

allocfail.sh

 #!/bin/sh
 
 # allocfail.sh -- Test for libbacktrace library.
-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2021 Free Software Foundation, Inc.
 
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are

atomic.c

 /* atomic.c -- Support for atomic functions if not present.
-   Copyright (C) 2013-2020 Free Software Foundation, Inc.
+   Copyright (C) 2013-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

backtrace-supported.h.in

 /* backtrace-supported.h.in -- Whether stack backtrace is supported.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

backtrace.c

 /* backtrace.c -- Entry point for stack backtrace library.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

backtrace.h

 /* backtrace.h -- Public header file for stack backtrace library.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

btest.c

 /* btest.c -- Test for libbacktrace library
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

configure.ac

 # configure.ac -- Backtrace configure script.
-# Copyright (C) 2012-2020 Free Software Foundation, Inc.
+# Copyright (C) 2012-2021 Free Software Foundation, Inc.
 
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are

dwarf.c

 /* dwarf.c -- Get file/line information from DWARF for backtraces.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

edtest.c

 /* edtest.c -- Test for libbacktrace storage allocation stress handling
-   Copyright (C) 2017-2020 Free Software Foundation, Inc.
+   Copyright (C) 2017-2021 Free Software Foundation, Inc.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are

edtest2.c

 /* edtest2.c -- Test for libbacktrace storage allocation stress handling (p2)
-   Copyright (C) 2017-2020 Free Software Foundation, Inc.
+   Copyright (C) 2017-2021 Free Software Foundation, Inc.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are

elf.c

 /* elf.c -- Get debug data from an ELF file for backtraces.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

fileline.c

 /* fileline.c -- Get file and line number information in a backtrace.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

install-debuginfo-for-buildid.sh.in

@@ -2,7 +2,7 @@
 
 # install-debug-info-for-buildid.sh -- Helper script for libbacktrace library
 # testing.
-# Copyright (C) 2019-2020 Free Software Foundation, Inc.
+# Copyright (C) 2019-2021 Free Software Foundation, Inc.
 
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are

instrumented_alloc.c

 /* instrumented_alloc.c -- Memory allocation instrumented to fail when
    requested, for testing purposes.
-   Copyright (C) 2018-2020 Free Software Foundation, Inc.
+   Copyright (C) 2018-2021 Free Software Foundation, Inc.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are

internal.h

 /* internal.h -- Internal header file for stack backtrace library.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

macho.c

 /* elf.c -- Get debug data from a Mach-O file for backtraces.
-   Copyright (C) 2020 Free Software Foundation, Inc.
+   Copyright (C) 2020-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

mmap.c

 /* mmap.c -- Memory allocation with mmap.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

mmapio.c

 /* mmapio.c -- File views using mmap.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

mtest.c

 /* mtest.c -- Minidebug test for libbacktrace library
-   Copyright (C) 2020 Free Software Foundation, Inc.
+   Copyright (C) 2020-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

nounwind.c

 /* backtrace.c -- Entry point for stack backtrace library.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

pecoff.c

 /* pecoff.c -- Get debug data from a PE/COFFF file for backtraces.
-   Copyright (C) 2015-2020 Free Software Foundation, Inc.
+   Copyright (C) 2015-2021 Free Software Foundation, Inc.
    Adapted from elf.c by Tristan Gingold, AdaCore.
 
 Redistribution and use in source and binary forms, with or without

posix.c

 /* posix.c -- POSIX file I/O routines for the backtrace library.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

print.c

 /* print.c -- Print the current backtrace.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

read.c

 /* read.c -- File views without mmap.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

simple.c

 /* simple.c -- The backtrace_simple function.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

sort.c

 /* sort.c -- Sort without allocating memory
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

state.c

 /* state.c -- Create the backtrace state.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

stest.c

 /* stest.c -- Test for libbacktrace internal sort function
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

test_format.c

 /* test_format.c -- Test for libbacktrace library
-   Copyright (C) 2018-2020 Free Software Foundation, Inc.
+   Copyright (C) 2018-2021 Free Software Foundation, Inc.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are

testlib.c

 /* testlib.c -- test functions for libbacktrace library
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

testlib.h

 /* testlib.h -- Header for test functions for libbacktrace library
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

ttest.c

 /* ttest.c -- Test for libbacktrace library
-   Copyright (C) 2017-2020 Free Software Foundation, Inc.
+   Copyright (C) 2017-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

unittest.c

 /* unittest.c -- Test for libbacktrace library
-   Copyright (C) 2018-2020 Free Software Foundation, Inc.
+   Copyright (C) 2018-2021 Free Software Foundation, Inc.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are

unknown.c

 /* unknown.c -- used when backtrace configury does not know file format.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

xcoff.c

 /* xcoff.c -- Get debug data from an XCOFF file for backtraces.
-   Copyright (C) 2012-2020 Free Software Foundation, Inc.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
    Adapted from elf.c.
 
 Redistribution and use in source and binary forms, with or without

xztest.c

 /* xztest.c -- Test for libbacktrace LZMA decoder.
-   Copyright (C) 2020 Free Software Foundation, Inc.
+   Copyright (C) 2020-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without

ztest.c

 /* ztest.c -- Test for libbacktrace inflate code.
-   Copyright (C) 2017-2020 Free Software Foundation, Inc.
+   Copyright (C) 2017-2021 Free Software Foundation, Inc.
    Written by Ian Lance Taylor, Google.
 
 Redistribution and use in source and binary forms, with or without