HLSL: Avoid leaking a shadow sampler struct

Avoid leaking name for counter buffer

HLSL: Fix #1655; use "" for nullptr file names

Work around a CMake cross-compilation issue

Update SPIRV-Tools known good: relax Uconvert check

Permit UConvert as an OpSpecConstantOp operation when
SPV_AMD_gpu_shader_int_16 is used.

Parenthesize to avoid GCC warning

Don't output duplicate OpTypeAccelerationStructureNV declarations

GL_EXT_buffer_reference

* Make sure source strings are terminated

The source strings may or may not have a null terminator. We need to
make sure we add one before outputting the source strings as we iterate
over the c-str looking for the null terminator.

* Review feedback

Mark spv.int16.amd.frag.out as failing validation

See #1642

Also updates SPIRV-Tools and SPIRV-Headers known_good.

CMake can't correctly configure the latest code because of an issue with
cross-compilation of pthreads:
https://gitlab.kitware.com/cmake/cmake/issues/16920

Create separate OpSource for each included file when compiling -g

Add passes to spirv-opt passes to preserve source line info when compiling -g.

CMake: Fix linking pthread of CMake < 3.1

As reported in #1624, Ubuntu 14.04 LTS still uses CMake 2.8.12 which
does not support the Threads::Threads target (added in CMake 3.1).

This could be reverted once the required CMake version is bumped to 3.1+.

Move memory model scope tests to Vulkan 1.1 batch

Fixes #1610

* Updated expected result due to version change

Fixes #1630 and fixes #1631.

Fix bug where shaderRecordNV buffers were using StorageBuffer storage class

From internal Khronos discussions, work, and testing.

Update to newest SPIRV-Tools, emit default Binding decoration.

Update to newest SPIRV-Tools. It checks the Vulkan rule that all resources must have a set and binding decoration, which many tests fail. So add code to set a default value of zero. Also disable PCH for Ninja builds.

Add to README: git config --global core.fileMode false

Remove Unix executable permission from text files