This partially addressess issue #670, for when the matrix swizzle
degenerates to a component or column: m[c], m[c][r] (where HLSL
swaps rows and columns for user's view).

An error message is given for the arbitrary cases not covered.

These cases will work for arbitrary use of l-values.

Future work will handle more arbitrary swizzles, which might
not work as arbitrary l-values.

This encapsulates where the string could overflow, removing 40 lines
of fragile code.  It also improves handling of numbers that are too long.

There are a couple of open issues that could related to this function
being more rational (locale dependence, 1.#INF).

add other builtins to interstage IO

Includer interface change to support full include semantics (requires downstream changes)

Add a CMake option to disable compilation of HLSL input support.

Matches existing options.

(Still adding tests: do not commit)

This fixes PR #632 so that:

(a) The 4 PerVertex builtins are added to an interface block for all stages except fragment.

(b) Other builtin qualified variables are added as "loose" linkage members.

(c) Arrayness from the PerVertex builtins is moved to the PerVertex block.

(d) Sometimes, two PerVertex blocks are created, one for in, one for out (e.g, for some GS that
    both reads and writes a Position)

Address several compiler warnings

Reorder initializer fields to match variable declaration order (or vice versa) for several class constructors.

Any previous use would only be for "", which would probably mean changing

    include(...)  -> includeLocal(...)

See comments about includeLocal() being an additional search over
includeSystem(), not a superset search.

This also removed ForbidIncluder, as
 - the message in ForbidIncluder was redundant: error results were
   already returned to the caller, which then gives the error it
   wants to
 - there is a trivial default implementation that a subclass can
   override any subset of (I still like abstract base classes though)
 - trying to get less implementation out of the interface file anyway

This is versus a variety of file-related language, designated, requested, etc.
Will simplify diffs for next commit.

- fixed ParseHelper.cpp newlines (crlf -> lf)
- removed trailing white space in most source files
- fix some spelling issues
- extra blank lines
- tabs to spaces
- replace #include comment about no location

PP: #include: simplify the different paths out of #include.

- some paths didn't release 'res'
- token is always '\n' after proper acceptance of the directive itself,
  so no need to test it, change it to '\n', etc.
- assuming setCurrentColumn(0) is not needed unless there are header tokens,
  but not clear why it is ever needed

Note: much of the simplified code read as if the included header tokens had
actually been processed, versus queued up for processing; maybe that explains
some things.

HLSL: allow destination swizzles when writing RWTexture/RWBuffer

This also makes it match how GLSL handles the same thing.

HLSL: allow type keywords as identifiers, and add half type

HLSL: inter-stage structure splitting.

Add D3DCOLORtoUBYTE4 decomposition

HLSL: default function parameters

Also correctly test and handle missing newline.

Reads and write syntax to UAV objects is turned into EOpImageLoad/Store
operations.  This translation did not support destination swizzles,
for example, "mybuffer[tc].zyx = 3;", so such statements would fail to
compile.  Now they work.

Parial updates are explicitly prohibited.

New test: hlsl.rw.swizzle.frag

This PR adds support for default function parameters in the following cases:

1. Simple constants, such as void fn(int x, float myparam = 3)
2. Expressions that can be const folded, such a ... myparam = sin(some_const)
3. Initializer lists that can be const folded, such as ... float2 myparam = {1,2}

New tests are added: hlsl.params.default.frag and hlsl.params.default.err.frag
(for testing error situations, such as ambiguity or non-const-foldable).

In order to avoid sampler method ambiguity, the hlsl better() lambda now
considers sampler matches.  Previously, all sampler types looked identical
since only the basic type of EbtSampler was considered.

HLSL allows type keywords to also be identifiers, so a sequence such as "float half = 3" is
valid, or more bizzarely, something like "float.float = int.uint + bool;"

There are places this is not supported.  E.g, it's permitted for struct members, but not struct
names or functions.  Also, vector or matrix types such as "float3" are not permitted as
identifiers.

This PR adds that support, as well as support for the "half" type.  In production shaders,
this was seen with variables named "half".  The PR attempts to support this without breaking
useful grammar errors such as "; expected" at the end of unterminated statements, so it errs
on that side at the possible expense of failing to accept valid constructs containing a type
keyword identifier.  If others are discovered, they can be added.

Also, half is now accepted as a valid type, alongside the min*float types.

This commit adds support for copying nested hierarchical types of split
types.  E.g, a struct of a struct containing both user and builtin interstage
IO variables.

When copying split types, if any subtree does NOT contain builtin interstage
IO, we can copy the whole subtree with one assignment, which saves a bunch
of AST verbosity for memberwise copies of that subtree.