GLSL: apply unused variable

Disabled MSVC 2015 compile warnings.

I happened upon numArgs while hunting for unused variables. I suspect
the intent was to apply it as shown in this patch. However, I am not a
compiler dude. Someone more appropriate should grok this change.

HLSL: fix defect in EOpMethodSampleCmp* texture decomposition

HLSL: phase 4 of RWTexture support: add image atomics

HLSL: Fix unary and binary operator type conversion issues

SPV: Add missing guard to code that uses AMD extensions

HLSL holds the compare value in a separate intrinsic arg, but the AST wants
a vector including the cmp val, except in the 4-dim coord case, where it
doesn't fit and is in fact a separate AST parameter.  This is awkward but
necessary, given AST semantics.  In the process, a new vector is constructed
for the combined result, but this vector was not being given the correct
TType, so was causing some downstream troubles.

Now it is.  A similar defect existed in OpTextureBias, and has also been
fixed.

A need arose to use capabilities from TIntermediate during
node promotion.  These methods have been moved from virtual
methods on the TIntermUnary and TIntermBinary nodes to methods
on TIntermediate, so it is easy for them construct new nodes
and so on.

This is done as a separate commit to verify that no test results
are changed as a result.

This PR will turn Interlocked* intrinsics using rwtexture or rwbuffer
object as the first parameter into the proper OpImageAtomic* operations.

Otherwise compilation fails when ENABLED_AMD_EXTENSIONS is off.

This fixes defects as follows:

1. handleLvalue could be called on a non-L-value, and it shouldn't be.

2. HLSL allows unary negation on non-bool values.  TUnaryOperator::promote
   can now promote other types (e.g, int, float) to bool for this op.

3. HLSL allows binary logical operations (&&, ||) on arbitrary types, similar
   (2).

4. HLSL allows mod operation on arbitrary types, which will be promoted.
   E.g, int % float -> float % float.

VS2010 compile fixes

HLSL: phase 3 of rwtexture support: add sub-vec4 capabilities

Use pthread_mutex for global lock on Linux.

SPV: Add missing extension declarations for certain AMD extensions.

HLSL: allow multi-dimensional arrays

This uses the Unknown storage format, instead of deducing the
format from the texture declaration type.

Also makes a (correct) test change for global -> temp vars.

This PR sets the TQualifier layoutFormat according to the HLSL image type.
For instance:

  RWTexture1D <float2> g_tTex1df2;

becomes ElfRg32f.  Similar on Buffers, e.g, Buffer<float4> mybuffer;

The return type for image and buffer loads is now taken from the storage format.
Also, the qualifier for the return type is now (properly) a temp, not a global.

HLSL: phase 2: add operator[]

Check for out-of-range bindings during IO mapping.

All the underpinnings are there; this just parses multiple array dimensions
and passes them through to the existing mechanisms.

Also, minor comment fixes, and add a new test for multi-dim arrays.

* This avoids an internal compile error on VS2010 possibly related to
  std::enable_if use.