* fix working on mac clock_gettime

* Comment fixme

* Auto-detect whether to produce colorized output

Rename --color_print to --benchmark_color for consistency with the other
flags (and Google Test). Old flag name is kept around for compatibility.

The --benchmark_color/--color_print flag takes a third option, "auto",
which is the new default. In this mode, we attempt to auto-detect
whether to produce colorized output. (The logic for deciding whether to
use colorized output was lifted from GTest:
<https://github.com/google/googletest/blob/master/googletest/src/gtest.cc#L2925>.)

* Update CONTRIBUTORS, AUTHORS

If a reporter's output stream isn't line-buffered (e.g. it's not writing
to a terminal) then it can be some time before a write to it becomes
visible.

This is problematic if, say, you're wanting to use tail -f to view the
file written to via --benchmark_out. Or if the application crashes,
leaving you with no results.

Addressed by flushing the reporters' output streams whenever we invoke
methods that may write to them.

* Cleanup the code for generating and running benchmarks

* Rework calculation of real/manual time

* Add back TSAN builder

* Refactor benchmark.cc into benchmark_register.cc and benchmark_run.cc

The benchmark.cc file is getting really big and it contains a bunch of
unrelated components. This patch separates the files into two separate
parts. The "runtime" parts and the "registration" parts.

This patch also removes the PIMPL used by Benchmark. Previously we couldn't
have STL types in the interface but now we can. Therefore there is no reason
to keep BenchmarkImp.

* add missing include

* rework windows timers again

* Guard timespec on older Windows versions

* Remove old thread safety annotation workarounds

* add additive thread range

* add test

* Change to using per-thread timers

* fix bad assertions

* fix copy paste error on windows

* Fix thread safety annotations

* Make null-log thread safe

* remove remaining globals

* use chrono for walltime since it is thread safe

* consolidate timer functions

* Add missing ctime include

* Rename to be consistent with Google style

* Format patch using clang-format

* cleanup -Wthread-safety configuration

* Don't trust _POSIX_FEATURE macros because OS X lies.

* Fix OS X thread timings

* attempt to fix mingw build

* Attempt to make mingw work again

* Revert old mingw workaround

* improve diagnostics

* Drastically improve OS X measurements

* Use average real time instead of max

* Fixture: add non const Setup() and TearDown().

This allows write-access to the State variable, which is important in
upcoming user-defined counter functionality.

* Fix const placement in the Fixture methods.

* Fixture: use const_cast instead of static_cast.

cmake does not require this, but IDEs such as VisualStudio or QtCreator
need this to add the headers to the generated project.

* Add warning for large benchmark families

* reflow comment

* Add BENCHMARK_USE_LIBCXX option.

* Add comments

* re-add zero null pointer warning

* changes

* remove other changes

* remove unneeded test

* cleanup unused include