Added -C option to request cascading errors.  By default, will exit early,
to avoid all error-recovery-based crashes.

This works by simulating end-of-file in input on first error, so no
need for exception handling, or stack unwinding, or any complex error
checking/handling to get out of the stack.

Added -x option to save SPIR-V as 32-bit hexadecimal numbers to a text file.

Includes adding test cases to verify the differences.

This is used by OpenGL, but not Vulkan.
Includes:
 - atomicCounter, atomicIncrement, atomicCounterDecrement
 - atomic_uint layout-offset checking
 - AtomicStorage capability

HLSL: Add template style constructors for vector & matrix types

This fixes issue #360.

Also, improve variable names. This grew to be overly hard to understand.

Suggest gl_[Vertex,Instance]Index when gl_[Vertex,Instance]ID is encountered in Vulkan GLSL

See issue #350 for detail.  This may be an ESSL specification issue.

HLSL: Change intrinsics tests to not use overloaded entry points

When parsing Vulkan GLSL, suggest gl_VertexIndex/gl_InstanceIndex instead of gl_VertexID/gl_InstanceID.

SPV: Certain decorations are missing for structure-typed in/out variables

HLSL: Add asdouble, fma, & mad intrinsics 

Remove duplicated tests from the runtests script.

Basic (component) type conversion was done, but checking that the composite
was correct was not being done.

Fixes issue #353.

This is to make the real change needed in the next commit easier.

Symbol table sharing has different sets of symbols for different
versions. This needs to take into account that SPIR-V has different
symbols than non-SPIR-V.

HLSL: Add lerp, fix sincos ret, add ret type tests, non-square mats, tx semantics

Front-end: allow max size built-in arrays like gl_ClipDistance

Fixed off-by-one error with gl_MaxClipDistances and similar limits.