HLSL: implemented c register handling

HLSL: fix invalid spir-v vector * scalar for float1

Updated type conversion rules for HLSL frontend

Missing check for float results in always emitting OpIMul even for float types

Adjusted a test not to use c register for
a structured buffer, they are supposed to
use t registers

Added comments with hints for what are the
register types are used for.

Handle potentially uninitialized result

PCH filename depends on current binary dir

Fixes #1572

Fix parser issue: redeclare gl_FragStencilRefARB is not supported

Apinheiro/xfb struct assignment

Add DeadBranchElim before MergeReturn in legalization.

MergeReturn now requires this or could throw an error.

Rename PCH macro to glslang_pch (to avoid name collision) and update to latest spirv-tools

Use precompiled headers for some glslang projects (MSVC-only)

Add names for composite spec constants in SPIR-V

Consider the following code:

    layout(constant_id=0) const int Y = 1;
    layout(constant_id=1) const int Z = 2;
    layout(constant_id=3) const int X = Y + Z;

Previously, it would produce SPIR-V decorations like this:

    Decorate 21(Y) SpecId 1
    Decorate 22 SpecId 3
    Decorate 33(Z) SpecId 0

This seems inaccurate, since the spec constant `X` that is dependent on
the two others did not get a name in the SPIR-V decorations. This behavior
may potentially negatively affect shader introspection capabilities.

This change alters the behavior to always add a name, which results in the code
above producing the following decorations:

    Decorate 21(Y) SpecId 1
    Decorate 22(X) SpecId 3
    Decorate 33(Z) SpecId 0

Add support for nv_ray_tracing final 

If the out variable is a struct type, with a xfb_offset explicitly
assigned, the members need to get their xfb_offset assigned. This is
specially relevant, as we cannot use layout qualifiers on struct
members.

BUILD.gn: remove reference to non-existent header

Fix MSVC warning C4065: 'default' but no 'case' labels

This would happen in SpvPostProcess when we don't enable AMD extensions.

Fix 8-bit storage nearly always using the UniformAndStorageBuffer8BitAccess capability.

Allow GL_NV_mesh_shader in fragment shaders for perprimitiveNV

UniformAndStorageBuffer8BitAccess capability.

When using the 8-bit storage extension it basically always used the
`UniformAndStorageBuffer8BitAccess` capability, even in cases where it
wasn't required. For instance if we are targeting Vulkan 1.1 (SPIR-V 1.3
or higher), and we are only using 8-bit types in an SSBO, we only need
the `StorageBuffer8BitAccess` capability.

I fixed this by enabling storage buffer use in Vulkan 1.1 / SPIR-V 1.3
or higher, and then changing the logic to match.

I also added some tests that will output different capabilities when run
on Vulkan 1.0 and 1.1, thus they are added twice to the test list (one
for each version).

Fixes #1539

- Emit relevant capability/extension for use of perprimitiveNV in fragment shader
- Remove redundant checks for mesh shader qualifiers in glslang.y
- Add profile version check for use of extension GL_NV_mesh_shader
- Add a new gtest for use of perprimitiveNV in fragment shader

Fixup unused parameter warnings