HLSL: add f16tof32 and f32tof16 decompositions.

These correspond to SPV_KHR_device_group and SPV_KHR_multiview.
Also, bring tests up to date with Khronos internals, and some misc. related changes.

Add reflection queries for thread local size.  Add ssbo auto-binding.

SPV: Unexpected declarations of capabilities from NV extensions.

New command line option --shift-ssbo-binding mirrors --shift-ubo-binding, etc.

New reflection query getLocalSize(int dim) queries local size, e.g, CS threads.

HLSL: implement 4 (of 6) structuredbuffer types

This is a partial implemention of structurebuffers supporting:

* structured buffer types of:
*   StructuredBuffer
*   RWStructuredBuffer
*   ByteAddressBuffer
*   RWByteAddressBuffer

* Atomic operations on RWByteAddressBuffer

* Load/Load[234], Store/Store[234], GetDimensions methods (where allowed by type)

* globallycoherent flag

But NOT yet supporting:

* AppendStructuredBuffer / ConsumeStructuredBuffer types
* IncrementCounter/DecrementCounter methods

Please note: the stride returned by GetDimensions is as calculated by glslang for std430,
and may not match other environments in all cases.

Add override where needed by clang++

Otherwise we get an error when we have both
-Werror and -Winconsistent-missing-override.
This is required for building with NDK r14 betas

Implement GL_EXT_shader_image_load_formatted

HLSL - Support for SV_GroupIndex

Update from master

Added --vn option to generate a C header file containing a variable a…

Fix mismatched doc string for SPV_KHR_subgroup_vote

Text for opcodes OpSubgroupAllKHR and OpSubgroupAnyKHR was swapped.

Implement NVX_multiview_per_view_attributes

Add basic HS/DS implementation.

This obsoletes WIP PR #704, which was built on the pre entry point wrapping master.  New version
here uses entry point wrapping.

This is a limited implementation of tessellation shaders.  In particular, the following are not functional,
and will be added as separate stages to reduce the size of each PR.

* patchconstantfunctions accepting per-control-point input values, such as
  const OutputPatch <hs_out_t, 3> cpv are not implemented.

* patchconstantfunctions whose signature requires an aggregate input type such as
  a structure containing builtin variables.  Code to synthesize such calls is not
  yet present.

These restrictions will be relaxed as soon as possible.  Simple cases can compile now: see for example
Test/hulsl.hull.1.tesc - e.g, writing to inner and outer tessellation factors.

PCF invocation is synthesized as an entry point epilogue protected behind a barrier and a test on
invocation ID == 0.  If there is an existing invocation ID variable it will be used, otherwise one is
added to the linkage.  The PCF and the shader EP interfaces are unioned and builtins appearing in
the PCF but not the EP are also added to the linkage and synthesized as shader inputs.
Parameter matching to (eventually arbitrary) PCF signatures is by builtin variable type.  Any user
variables in the PCF signature will result in an error.  Overloaded PCF functions will also result in
an error.

[domain()], [partitioning()], [outputtopology()], [outputcontrolpoints()], and [patchconstantfunction()]
attributes to the shader entry point are in place, with the exception of the Pow2 partitioning mode.

SPV: Emit op select

Also, ensures it has a type, no disallowed side effects,
or performance trade offs.

HLSL: Wrap entry-point; needed to write 'in' args, and support 'inout' args

This enables the IO type mapping to work transparently for typedefs.