Add support for GL_OES_EGL_image_external_essl3

HLSL: allow split type in InputPatch template type, & HS return types.

InputPatch parameters to patch constant functions were not using the
internal (temporary) variable type.  That could cause validation errors
if the input patch had a mixture of builtins and user qualified members.

This uses the entry point's internal form.

There is currently a limitation: if an InputPatch is used in a PCF,
it must also have appeared in the main entry point's parameter list.
That is not a limitation of HLSL.  Currently that situation is detected
and an "implemented" error results.  The limitation can be addressed,
but isn't yet in the current form of the PR.

Hull shaders have an implicitly arrayed output.  This is handled by creating an arrayed form of the
provided output type, and writing to the element of it indexed by InvocationID.

The implicit indirection into that array was causing some troubles when copying to a split
structure.  handleAssign was able to handle simple symbol lvalues, but not an lvalue composed
of an indirection into an array.

There was some ambiguity/contradiction in this behavior, and
Khronos decided glslang should always have these outside blocks,
rather than have stage/vendor/target variations.

GLSL: Promote HLSL entry-point renaming code to be used by GLSL as well.

Fixes #1045.

Implement the extension GL_AMD_shader_fragment_mask

Build: Fix strdup -> _strdup warnings.

Delete unused 'this' capture

Remove an unused 'this' entry from a lambda capture list.

This cleans up a unused-lambda-capture warning.

Add stdin option (fixes #598)

Fix lvalue test in SPIR-V generation

There were several locations in TGlslangToSpvTraverser::handleUserFunctionCall testing for
whether a fn argument should be in the lvalue or rvalue array.  They must get the same
result for indexing sanity, but had slightly different logic.

They're now forced into the same test.

WIP: Linux build warning fix

Fix issues of GL_ARB_viewport_layer_array

* Remove complaint about unused function parameter in resolveUniformLocation()
* Remove complaint about defined but not used variable in spvIR.h

HLSL: add geometry stage support for clip/cull distance

Changes:

(1) Allow clip/cull builtins as both input and output in the same shader stage.  Previously,
not enough data was tracked to handle this.

(2) Handle the extra array dimension in GS inputs.  The synthesized external variable can
now be created with the extra array dimension if needed, and the form conversion code is
able to handle it as well.

For example, both of these GS inputs would result in the same synthesized external type:

    triangle in float4 clip[3] : SV_ClipDistance

    triangle in float2 clip[3][2] : SV_ClipDistance

In the second case, the inner array dimension packs with the 2-vector of floats into an array[4],
which there is an array[3] of due to the triangle geometry.

HLSL: fix preprocessor concatenation behaviour.

Fix #772.

HLSL: (minor) fix type on clip/cull index result

While adding geometry stage support for clip/cull, it transpired that the
existing clip/cull support was not setting the type of the result of indexing
into the clup/cull variable.  That's a defect independent of the geometry
support, so to simplify the geometry PR, this is addressed separately.

It doesn't appear to change the generated SPIR-V, but that's probably down to
something else tolerating a bad input.

Fix #1019.

Fix #1020. Fix #1021. Fix #1022.

SPV: 1st pass implementation of SPV_EXT_shader_viewport_index_layer.