This wasn't needed until the recent generalization of "main" to "entry point",
so makes some HLSL-specific code be generic now, for GLSL functional correctness.

HLSL: Recursive composite flattening

HLSL: opcode specific promotion rules for interlocked ops

GLSL: Always define TShader::~Includer().

This PR implements recursive type flattening.  For example, an array of structs of other structs
can be flattened to individual member variables at the shader interface.

This is sufficient for many purposes, e.g, uniforms containing opaque types, but is not sufficient
for geometry shader arrayed inputs.  That will be handled separately with structure splitting,
 which is not implemented by this PR.  In the meantime, that case is detected and triggers an error.

The recursive flattening extends the following three aspects of single-level flattening:

- Flattening of structures to individual members with names such as "foo[0].samp[1]";

- Turning constant references to the nested composite type into a reference to a particular
  flattened member.

- Shadow copies between arrays of flattened members and the nested composite type.

Previous single-level flattening only flattened at the shader interface, and that is unchanged by this PR.
Internally, shadow copies are, such as if the type is passed to a function.

Also, the reasons for flattening are unchanged.  Uniforms containing opaque types, and interface struct
types are flattened.  (The latter will change with structure splitting).

One existing test changes: hlsl.structin.vert, which did in fact contain a nested composite type to be
flattened.

Two new tests are added: hlsl.structarray.flatten.frag, and hlsl.structarray.flatten.geom (currently
issues an error until type splitting is online).

The process of arriving at the individual member from chained postfix expressions is more complex than
it was with one level.  See large-ish comment above HlslParseContext::flatten() for details.

PR #577 addresses most but not all of the intrinsic promotion problems.
This PR resolves all known cases in the remainder.

Interlocked ops need special promotion rules because at the time
of function selection, the first argument has not been converted
to a buffer object.  It's just an int or uint, but you don't want
to convert THAT argument, because that implies converting the
buffer object itself.  Rather, you can convert other arguments,
but want to stay in the same "family" of functions.  E.g, if
the first interlocked arg is a uint, use only the uint family,
never the int family, you can convert the other args as you please.

This PR allows making such opcode and arg specific choices by
passing the op and arg to the convertible lambda.  The code in
the new test "hlsl.promote.atomic.frag" would not compile without
this change, but it must compile.

Also, it provides better handling of downconversions (to "worse"
types), which are permitted in HLSL.  The existing method of
selecting upconversions is unchanged, but if that doesn't find
any valid ones, then it will allow downconversions.  In effect
this always uses an upconversion if there is one.

Rather than update the existing ifdef to cover all necessary cases,
get rid of it and always define TShader::~Includer().

runtests should refer to test files in current directory

Fixes issue #239.

Fixed processing #include's when preprocessing HLSL

Recently added entry point renaming file referred to
test source file hlsl.entry.rename.frag via relative directory.

Change it to be consistent with other tests: assume test
sources are in the current directory.

Merge branch 'intrinsic-promotion' of https://github.com/steve-lunarg/glslang into steve-lunarg-intrinsic-promotion

HLSL: allow renaming of shader entry point when creating SPIR-V

Use "--source-entrypoint name" on the command line, or the
TShader::setSourceEntryPoint(char*) API.

When the name given to the above interfaces is detected in the
shader source, it will be renamed to the entry point name supplied
to the -e option or the TShader::setEntryPoint() method.

This highly leverages the previous commit to handle partial initializers.

This PR handles implicit promotions for intrinsics when there is no exact match,
such as for example clamp(int, bool, float).  In this case the int and bool will
be promoted to a float, and the clamp(float, float, float) form used.

These promotions can be mixed with shape conversions, e.g, clamp(int, bool2, float2).

Output conversions are handled either via the existing addOutputArgumentConversion
function, which this PR generalizes to handle either aggregates or unaries, or by
intrinsic decomposition.  If there are methods or intrinsics to be decomposed,
then decomposition is responsible for any output conversions, which turns out to
happen automatically in all current cases.  This can be revisited once inout
conversions are in place.

Some cases of actual ambiguity were fixed in several tests, e.g, spv.register.autoassign.*

Some intrinsics with only uint versions were expanded to signed ints natively, where the
underlying AST and SPIR-V supports that.  E.g, countbits.  This avoids extraneous
conversion nodes.

A new function promoteAggregate is added, and used by findFunction.  This is essentially
a generalization of the "promote 1st or 2nd arg" algorithm in promoteBinary.

The actual selection proceeds in three steps, as described in the comments in
hlslParseContext::findFunction:

1. Attempt an exact match.  If found, use it.
2. If not, obtain the operator from step 1, and promote arguments.
3. Re-select the intrinsic overload from the results of step 2.

A way to query "location" qualifier for vertex attributes, using TProgram reflection API

HLSL: Add GS support

HLSL: use HLSL parser for HLSL intrinsic prototypes, enable int/bool mats

HLSL: allow "sample" as a valid identifier.

Adding a way to retrieve vertex attribute TType using TProgram reflection API (required in order to query location attributes).

This PR adds:

[maxvertexcount(n)] attributes

point/line/triangle/lineadj/triangleadj qualifiers

PointStream/LineStream/TriangleStream templatized types

Append method on above template types

RestartStrip method on above template types.

HLSL has keywords for various interpolation modifiers such as "linear",
"centroid", "sample", etc.  Of these, "sample" appears to be special,
as it is also accepted as an identifier string, where the others are not.

This PR adds this ability, so the construct "int sample = 42;" no longer
produces a compilation error.

New test = hlsl.identifier.sample.frag

This PR adds a CreateParseContext() fn analogous to CreateBuiltInParseables(),
to create a language specific built in parser.  (This code was present before
but not encapsualted in a fn).  This can now be used to create a source language
specific parser for builtins.

Along with this, the code creating HLSL intrinsic prototypes can now produce
them in HLSL syntax, rather than GLSL syntax.  This relaxes certain prior
restrictions at the parser level.  Lower layers (e.g, SPIR-V) may still have
such restrictions, such as around Nx1 matrices: this code does not impact
that.

This PR also fleshes out matrix types for bools and ints, both of which were
partially in place before.  This was easier than maintaining the restrictions
in the HLSL prototype generator to avoid creating protoypes with those types.

Many tests change because the result type from intrinsics moves from "global"
to "temp".

Several new tests are added for the new types.

Add UAV (image) binding offset and HLSL register class support

SPV: The execution scope for barriers should be Workgroup.