Also beefed up support for running compute shaders is #version 420, but this
work is only partially done.

Make two more IncludeResult members const.

SPV: Don't shadow sampler parameters when performing function calls

Link: Handle multiple ES profile compilation units for a single shader stage

Fixes #179

The test result should only give one error about linking
ES and non-ES shading language compilation units:

 - empty.frag: No version info, interpreted as 100, ES
 - empty2.frag: No version info, interpreted as 100, ES
 - empty3.frag: Version declared as 110, non-ES

Previously, because the new intermediate is always created
without version/profile information, there would be two
linker errors:

 1.) When merging the new intermediate with empty.frag
 2.) When merging (new intermediate + empty.frag + empty2.frag) with empty3.frag

Now, there is only one error; as the error with merging the
new intermediate with empty.frag has been removed.

When linking multiple compilation units per shader stage,
the code creates a new intermediate, but fails to set its
version and profile.

This change makes it so that the new intermediate inherits
the version and profile of the first compilation unit, so
that two ES SL compilation units can be combined.

Vulkan: Finish semantics for what creates spec-const-semantics.

Note: This required adding a new test mode to see the AST for vulkan tests.
This also required reworking some deeper parts of type creation, regarding
when storage qualification and constness is deduced bottom-up or dictated
top-down.

HLSL: Add base class TParseables for intrinsic / builtin generation.

Add stubbed HLSL derivation.  GLSL derivation is still called TBuiltIns,
for historical compatibility.

SPV: Fix an issue of interpolation decoration.

GLSL interpolation qualifiers and auxiliary storage qualifiers are not
mutually exclusive. So when they are translated to SPIR-V decorations, two
independent utility methods should be employed to do this job.

Fixes issue #252.

Build: atoi comes from stddef.h or cstddef

This is required to fix the Android build for ARM.

Test compiling shaders with given resource limits using GTest.

Fix the slow down in noContraction propagation

There have been GLSL extensions considering this, and HLSL does it.
This is a fully backward compatible change that allows this distinction.

Addresses issue #205.
Current open Khronos bug for finalizing this.

Nonfunctional: Remove declaration for ShGetPhysicalAttributeBindings

The function ShGetPhysicalAttributeBindings() is declared in the
header, but not defined (or referenced) anywhere in the codebase.

Reflection: Add support for querying vertex attributes in reflection API

Parser: Redeclaration of gl_CullDistance is disallowed mistakenly.

Testing: Add link tests in the GTest framework

SPV: Fix missing location decoration for structures put directly on input/output interfaces

Spec for decorating the OpVariable:
	"The remaining variables listed by OpEntryPoint with the Input or Output storage class form the user-defined variable interface. These variables must be identified with a Location decoration"

Spec for decorating struct type:
	"The layout of a structure type used as an Input or Output depends on whether it is also a Block (i.e. has a Block decoration).
	If it is a not a Block, then the structure type must have a Location decoration"