Rename GL_KHX_shader_explicit_arithmetic_types to GL_EXT_shader_expli…

GlslangToSpv: prevent add XfbStride twice

Without this commit, if the XfbStride was explicitly set, the
decoration was added twice on the shader.

v2 (changes after Jonh Kessenich first review)
   * Simplified by just removing the firs assignment
   * Removed assert

SPV: Generate OpArrayLength with no signedness.

This makes the rest of the AST consuming the result match GLSL
semantics and hence get complete type matching.

Add NDK build files

Also bump version for recent changes.

ParseHelper: assign global XfbBuffer to a block missing it

Implement GL_EXT_fragment_invocation_density

Add conversion folding when the source is a constant.

Update known good SPIRV tools and headers

* Fixes use of optimizer
* Updated test outputs
 * GeometryStreams and TransformFeedback no longer fail validation

including SPV generation using SPV_EXT_fragment_invocation_density.
This is an alias of the functionality in SPV_NV_shading_rate, and thus in some
cases we can only have one set of the tokens present (switch statements), so
we have picked the EXT version. This required updating the expected test
results for SPV_NV_shading_rate.

Also updated the known-good for spirv-headers so that the validator in
spirv-tools knows about the new extension.

This change adds unary conversion folding when the source is a constant.
This fixes an ISV issue whereby:

```
const float16_t f = float16_t(42.0);
```

Wouldn't compile because the conversion operator would always produce an
EvqTemporary when it could have produced an EvqConst.

I've also added a test case that proves out that all basic-type to
basic-type conversions work.

GLSL: Fix #1591: Require the id in subgroupBroadcast to be constant.

Update to newer SPIRV-Tools, including VK_EXT_scalar_block_layout

Validator has more refined messages about what kind of block layout
rules have been applied.

Merge branch 'scalar_block_layout' of https://github.com/jeffbolznv/glslang into jeffbolznv-scalar_block_layout

[HLSL/Spir-V] fix for incorrect spir-v on int dot(int, int)

Decomposes OpDot into corresponding multiplies and additions.

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