This adds TProgram::getUniformBlockCounterIndex(int index), which returns the
index the block of the counter buffer associated with the block of the passed in
index, if any, or -1 if none.

This is WIP, heavy on the IP part.  There's not yet enough to use in real workloads.

Currently present:

* Creation of separate counter buffers for structured buffer types needing them.
* IncrementCounter / DecrementCounter methods
* Postprocess to remove unused counter buffers from linkage
* Associated counter buffers are given @count suffix (invalid as a user identifier)

Not yet present:

* reflection queries to obtain bindings for counter buffers
* Append/Consume buffers
* Ability to use SB references passed as fn parameters

HLSL: Fix #672: Support 1.#INF and -1.#INF syntax.

Null-conversion needs the right sized vectors to kick out with matching types.

HLSL: fix return type for isfinite

The prior decomposition of isfinite was not setting the return type on the
sequence node.  (Sequence was used because there's an internal temporary
to avoid the complex rvalue problem).

Implement the extension SPV_KHR_16bit_storage

HLSL: cast bracket dereference index to int type if not.

HLSL can index arrays using operator[] with non-integer types, and
inserts a conversion to a uint if needed.

HLSL: allow non-vec3 tessellation coordinate declarations

Corresponds to the EShMsgHlslOffsets flag in messages.
Works for both GLSL and HLSL.

HLSL requires vec2 tessellation coordinate declarations in some cases
(e.g, isoline topology), where SPIR-V requires the TessCoord qualified
builtin to be a vec3 in all cases.  This alters the IO form of the
variable to be a vec3, which will be copied to the shader's declared
type if needed.  This is not a validation; the shader type must be correct.

C++11 features remove the dependencies from OS specific code. Changes:

- Making WorkList class to have its own mutex instead of the OS specific
global one. The new mutex is the one from std library. The OS specific
code is also removed.

- Using the C++11 std library to handle threads in StandAlone
application
and enabling concurrent processing on non-windows platforms.

- converting the global variable Worklist into local variable workList.

Somewhat complex due to recognizing a general scalar, but not
replicating it for each member to avoid side effects.

HLSL: Decompose OpIsFinite to avoid capability restrictions

Improves foundation for adding scalar casts.

Makes handle/make names more sane, better commented, uses more
precise subclass typing, and removes mutual recursion between
converting initializer lists and making constructors.

HLSL: Support InputPatch variables in patch constant functions

OpIsFinite is not available everywhere: decompose isfinite
to !isinf && !isnan.

Previously, patch constant functions only accepted OutputPatch.  This
adds InputPatch support, via a pseudo-builtin variable type, so that
the patch can be tracked clear through from the qualifier.

HLSL: fix GS to work with EP wrapping

The prior implementation of GS did not work with the new EP wrapping architecture.
This fixes it: the Append() method now looks up the actual output rather
than the internal sanitized temporary type, and writes to that.

HLSL: handle PCF input to DS in arbitrary argument position