This was done on GitHub, but lots of new code did not change when
doing the merge.

Implement the extension GL_AMD_gpu_shader_half_float_fetch

Fix issues of SPIRV headers

- Support new opaque types: f16sampler*, f16image*, f16subpassInput*.
- Add new built-in GLSL texture/image functions.

These are conditional now on which target environment is requested.

Note the tests do not yet generate the correct code regarding what extensions
they declare.

Fix typo in help for -V<bad-number>

EShLangFragment falls through to EShLangCompute, only #ifndef AMD_EXTENSIONS.

EShLangFragment falls through to EShLangCompute, only #ifndef AMD_EXTENSIONS.
This is probably a bug.

This factored computeTypeLocationSize() out of needing the TIntermediate contents,
and uses it to show how to know how many locations an object needs.
However, it still does not do cross stage, or mixed location/no-location
analysis.

Constants were generally cached by type opcode, but all structures share the
same type opcode (OpTypeStruct), so they need to be cached by type id.

I'm not yet clear if these are the right checks, but it puts
the right infrastructure and example in place.

Note: semantic checking against versions/extensions should happen earlier
than SPIR-V generation, so SPIR-V generation need only assume it is okay
to do what was asked.

This means the previously emitted code was incorrect.

Update known-good

See merge request GLSL/glslang!35

GLSL/SPV: Fix #1196: Require resources to have layout(binding=X).