SPV: Memory qualifiers should decorate top-level block members

HLSL: handle multiple clip/cull semantic IDs

HLSL allows several variables to be declared.  There are packing rules involved:
e.g, a float3 and a float1 can be packed into a single array[4], while for a
float3 and another float3, the second one will skip the third array entry to
avoid straddling

This is implements that ability.  Because there can be multiple variables involved,
and the final output array will often be a different type altogether (to fuse
the values into a single destination), a new variable is synthesized, unlike the prior
clip/cull support which used the declared variable.  The new variable name is
taken from one of the declared ones, so the old tests are unchanged.

Several new tests are added to test various packing scenarios.

Only two semantic IDs are supported: 0, and 1, per HLSL rules.  This is
encapsulated in

     static const int maxClipCullRegs = 2;

and the algorithm (probably :) ) generalizes to larger values, although there
are a few issues around how HLSL would pack (e.g, would 4 scalars be packed into
a single HLSL float4 out reg?  Probably, and this algorithm assumes so).

Fix dref explicit LOD form of sample with cube texture arrays

The dref parameter was being used as the LOD.  Now it it's properly the dref.

HLSL: Fix crash with --resource-set-binding [n] (global form, not per-register form)

--resource-set-binding has a mode which allows per-register assignments of
bindings and descriptor sets on the command line, and another accepting a
single descriptor set value to assign to all variables.

The former worked, but the latter would crash when assigning the values.
This fixes it, and makes the former case a bit more robust against premature
termination of the pre-register values, which must come in (regname,set,binding)
triples.

This also allows the form "--resource-set-binding stage setnum", which was
mentioned in the usage message, but did not parse.

The operation of the per-register form of this option is unchanged.

SPV: Decorate parameters

HLSL: Fix #980: flatten opaque initializers to use aliases.

Fix NULL pointer dereference in TParseContext::builtInOpCheck

Address part B of #982: $Global will use std140 instead of HLSL offsets.

From comment about this:
Adjust alignment for HLSL rules
TODO: make this consistent in early phases of code: adjusting this late means inconsistencies with earlier code, which for reflection is an issue.
Until reflection is brought in sync with these adjustments, don't apply to $Global,
which is the most likely to rely on reflection, and least likely to rely
implicit layouts.

HLSL: support global const initializers from non-constant rvalues

Fix StandAlone.cpp compilation warnings

find_first_of returns size_t, was overflowing int.

Semantic test left over from other source languages is removed, since this is permitted by HLSL.
Also, to support the functionality, a targeted test is performed for this case and it is
turned into a EvqGlobal qualifier to create an AST initialization segment when needed.

Constness is now propagated up aggregate chains during initializer construction.  This
handles hierarchical cases such as the distinction between:

    static const float2 a[2] = { { 1, 2 }, { 3, 4} };

vs

    static const float2 a[2] = { { 1, 2 }, { cbuffer_member, 4} };

The first of which can use a first class constant initalization, and the second cannot.

The multithreaded outputs in particular can be troublesome when searching.

HLSL: Translate directive [flatten] and [branch] to SPV control mask.

Implement SPV_KHR_post_depth_coverage

Added support for both extension GL_ARB_post_depth_coverage and GL_EXT_post_depth_coverage.

HLSL: handle type conversion for any/all intrinsics

HLSL allows float/etc types for any/all intrinsics, while the
SPIR-V opcode requires bool.  This adds a simple decomposition
to type convert the argument.  It could get a little more clever
in some of the type cases if it ever had to.

Add option to skip installation

Fix CMake scripts to set the POSITION_INDEPENDENT_CODE property correctly

Fix CMake scripts: The set_property script can be used to set only a single property, so now setting the POSITION_INDEPENDENT_CODE property correctly.