This contains the base for ray tracing extensions.

Forbid memoryBarrierAtomicCounter for Vulkan compiles

* Fixes #2005

Allow multiple units in a stage to have push_constants as long
as the blocks match.
Requires #2006 to be fixed to be functional.

* tweaks to #2005 fix after some testing

* add unit tests for push constants across multiple compilation units

For #2005

* update reference output for tests that fail validation

* fix uninitialized result.validationResult

When we use unsized array in shader storage buffer, glslang calculate the offset during delcaring the block, it may lead to incorrect block offsets when its implicit array size changed.

So here is what we do:
1. For GLSL, we add flag explicitOffset in TQualifier, and set it when layout offset is specified explicitly
2. By using this flag we could tell difference as whether it is an explicit offset, and recalculate the block member offset conditionally in OpenGL.

Fixes #2106

* Convert memcmps to strcmps

EXT_debug_printf - make escape sequences better match C/C++

Allow nonuniformEXT() on sampler types

disable escape sequences for #line and #error

This is conservative and still also decorates the loaded value.

Also add missing NonUniformEXT decoration on OpImageTexelPointer.

Fix typo in Web CMakeLists

Add Android build instructions to README

add c wrapper for standalone ResourceLimits and remove that dependency from glslang_c_interface

Fix for #2099: add c interface support for TBuiltInResource and glslang::DefaultTBuiltInResource

GL_EXT_debug_printf implementation

Includes an additional deprecation and rationalizing the beginning sections.

In GLSL/HLSL/AST,  v.zyx is an l-value, but not in SPIR-V, which cannot represent it.
So, a temporary is used instead.

This also made it obvious some code was (functionally correctly)
repeated, so deleted that too.

Add vcpkg installation instructions

Fix for #2075: removed DefaultTBuiltInResource from glslang_c_interface.cpp

Fix an issue of SPV generation for imageAtomicStore.

For GLSL function imageAtomicStore, it will be translated to
OpImageTexelPointer + OpAtomicStore. The result type of
OpImageTexelPointer must be the same as the sampled type of OpTypeImage.
On translation, the result type is mistakenly fetched from operand list
operands[2] while operands[2] corresponds to sampleNum whose type is
always uint. This leads to an error if the image type is iimageXXX that is
int image.

SPV_AMD_shader_image_load_store_lod is now validated by spirv-tools