GLSL/SPV: Fix #1900: Drop const on literal when doing an object copy.

Separate GLSLANG_WEB (min-size build) and Emscripten options

SPV_KHR_physical_storage_buffer/SPV: Add GL_EXT_buffer_reference_uvec2

Adds uvec2 <-> reference constructor support.
Switches from EXT to KHR for physical_storage_buffer.

Fix Fuchsia build.

The Fuchsia build is very picky about newlines at the end of files
and will complain loudly about them. Removing the -Wnewline-eof
warning solves the issue.

Allows building non-min-size builds with Emscripten.
Adds ENABLE_GLSLANG_WEB_DEVEL.
Moves the glslang.js files to OSDependent/Web.
Small cleanups and docs update.

Add GL_EXT_shader_subgroup_extended_types support

Branch to support SPIR-V 1.5 changes

The generalization to addIncorporatedExtension() also fixed a 1.3
corner case with SPV_KHR_16bit_storage.

Add flags for local size values ( compute shader )

Purpose :

According to GLSL SPEC 4.6 ( 4.4.1.4 Compute Shader Inputs), for compute shader input qualifiers, we should declare such qualifiers with same values in the same shader (local_size_x, y and z).
"If such a layout qualifier is declared more than once in the same shader, all those declarations must set the same set of local work-group sizes and set them to the same values; otherwise a compile-time error results."

Why this fix:

If we manually set "local_size_x = 1" and directly following a declaration like "local_size_x = 2", this would not be detected. That is because currently we treat all the '1' as default value and could not restrictly detect whether those are default values.

Test case:
......
layout(local_size_x=1) in;
layout(local_size_x=2) in;
......

So I add test cases for this fix:
1. set local_size_y = 1 => success
2. set local_size_y = 2 => error
3. set local_size_y = 1 => success

Comment out unused params; Fix type warning.

Fix incorrect function prototypes of 64-bit findLSB/findMSB

According to the 32-bit counterparts, their forms should be
genI64Type findLSB(genI64Type value)
genI64Type findLSB(genU64Type value)
genI64Type findMSB(genI64Type value)
genI64Type findMSB(genU64Type value)

The order of error checking was not quite being correct (maybe there is no correct
ordering, when many checks must be done and they affect each other).
So, check for block-name reuse twice.

Update spirv-tools and spriv-headers known good.

Code refine

Reduce the number of cycles.

Sync code

Sync code from KhronosGroup/glslang master

Also fixes, in practice, https://github.com/KhronosGroup/GLSL/issues/83.
When the specification language is correctly created, glslang can be
revisited for correctness.  In the meantime, this seems like the best
"bug" to have relative to the specification.

Memory qualifiers are only relevant to parameters when they apply
to what the argument points to, as otherwise the argument is copied.

This leaves the fix from #1870 in place, and then more correctly
ignores memory qualifiers when something will be passed by copy.

Initialize variable to avoid uninitialized variable warnings in Clang

In the current version of the code on non-debug builds these cases
will fallthrough, since assert is a no-op, and eventually make a call
passing in |op| which hasn't been initialized. clang is currently
throwing a warning about this behaviour when integrating downstream.

This patch changes the behaviour, so that in any branch that has an
assert now has a return nullptr, to indicate failure after it and
avoid the uninitialized variable usage.

GL_NV_integer_cooperative_matrix support