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

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.

- hlsl.struct.frag variable changed to static, assignment replacd.

- Created new low level functions addBinaryNode and addUnaryNode.  These are
  used by higher level functions such as addAssignment, and do not do any
  argument promotion or conversion of any sort.

- Two functions above are now used in RWTexture lvalue conversions.  Also,
  other direction creations of unary or binary nodes now use them, e.g, addIndex.
  This cleans up some existing code.

- removed handling of EOpVectorTimesScalar from promote()

- removed comment from ParseHelper.cpp

Improve comments.
A few tweaked lines allow [] on non-rw tx.  Add test case for this.
Improve VectorTimesScalar handling.

This commit splits lValueErrorCheck into machine dependent and independent
parts.  The GLSL form in TParseContext inherits from and invokes the
machine dependent part in TParseContextBase.  The base form checks language
independent things.  This split does not change the set of errors tested
for: the test results are identical.

The new base class interface is now used from the HLSL FE to test lvalues.
There was one test diff due to this, where the test was writing to a uniform.
It still does the same indirections, but does not attempt a uniform write.

This commit adds l-value support for RW texture and buffer objects.
Supported are:

- pre and post inc/decrement
- function out parameters
- op-assignments, such as *=, +-, etc.
- result values from op-assignments.  e.g, val=(MyRwTex[loc] *= 2);

Not supported are:
- Function inout parameters
- multiple post-inc/decrement operators.  E.g, MyRWTex[loc]++++;

This commit adds r-value support for RW textures and buffers.
Supported is:

- Function in parameter conversions
- conversion of rvalue use to imageLoad

SPV: Use SampledImage with OpImageQueryLod