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.

As a static target, when included in other cmake projects, it is not needed to install these libraries and headers as part of this build, and just need to link to this.

Multiview extension: Accept layout(num_views) qualifier

Lays the groundwork for fixing issue #954.

Partial flattenings were previously tracked through a stack of active subsets
in the parse context, but full functionality needs AST nodes to represent
this across time, removing the need for parsecontext tracking.

This commit, and next one, are specifically to make a future commit
handling partial dereferences of flattening objects easier to see.

io resolver improvements