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

Fix iomapper issue

Use type name to index map to instead of use instance name to index map, or anonymous block will cause a map issue.

HLSL: Fix part of #2070: Correctly handle promotion for <unary-op>(int).

This still only handles a scalar correctly, and some
vector cases need additional fixes.

Add an option to make RTTI enabled

CMake: Split "is emscripten" config from "enable glslang.js"

This should enable glslang to be used as a dependency of other projects
that target WebAssembly, instead of assuming "EMSCRIPTEN" => "Want
glslang.js".

Avoid enum-compare warning, missing cases in switch

GLSL: Support constant folding for mod

GLSL: Fix semantic error for GL_KHR_memory_scope_semantics

When 2DMS or 2DMSArray is used, IMAGE_PARAMS will take an additional
paramter to represent sample number. The semantics check should get the
correct semantics values, taking this case into account.

glslang.js: Make the SPIR-V target version configurable (1.0 ~ 1.5) and default to 1.0

Fix memory corruption in TGlslIoMapper

Use NOT ... VERSION_LESS instead of VERSION_GREATER_EQUAL

standalone: Fix --help

Fixes: bd97b6f9 ("Command-line: Give better error messages. From #1829.")
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>

Use correct enum type in case statement

Two similarly named enums led to the wrong one being used here, this
is getting caught in the Chromium and Dawn DEPS rolls.

Revisit fix for #2062 for consistency with this commit.