HLSL: allow uint literals, and add test for numeric suffixes

HLSL: Add CalculateLevelOfDetail, and unimplemented errors for *Uncla…

Missing are implicit conversions between int/bool/etc.

Starting out with this turned off, so tests can be locally fixed,
then will turn it on.

HLSL: add 2DMS texture formats, and matching Load / GetDimensions sup…

Apply the interpolation first, then apply the swizzle to the result,
the inverse of the order requested by the AST.  This fixes issue #411.

HLSL: Add gather, improve proto generator machine for upcoming 2DMS/S…

HLSL: enable #line extension by default for HLSL source.

Remapper: Remap Scope and MemorySemantics IDs in SPIRV remapper

Scope and MemorySemantics operands contain IDs as well and may need
remapping.

HLSL: Add SampleLevel method

Replaces PR #372.

Build: Add g++/clang warnings to match some enabled by /W4 in MSVC

HLSL: Add texture Load method & decomposition

AMD: Implement 4 AMD-specific extensions.

HLSL: Add SampleCmp and SampleCmpLevelZero texture methods

Also, the per-build part had stopped auto-updating,
which is fixed locally as a git hook.

- Support GL_AMD_shader_ballot (SPV_AMD_shader_ballot).
- Support GL_AMD_shader_trinary_minmax (SPV_AMD_shader_trinary_minmax).
- Support GL_AMD_shader_explicit_vertex_parameter
  (SPV_AMD_shader_explicit_vertex_parameter).
- Support GL_AMD_gcn_shader (SPV_AMD_gcn_shader).

Protect more against error recovery of bad built-in variable redeclarations.

HLSL: Add tx.GetDimensions method (uint returns only)