- 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.

This adds structure splitting, which among other things will enable GS support where input structs
are passed, and thus become input arrays of structs in the GS inputs.  That is a common GS case.

The salient points of this PR are:

* Structure splitting has been changed from "always between stages" to "only into the VS and out of
  the PS".  It had previously happened between stages because it's not legal to pass a struct
  containing a builtin IO variable.

* Structs passed between stages are now split into a struct containing ONLY user types, and a
  collection of loose builtin IO variables, if any.  The user-part is passed as a normal struct
  between stages, which is valid SPIR-V now that the builtin IO is removed.

* Internal to the shader, a sanitized struct (with IO qualifiers removed) is used, so that e.g,
  functions can work unmodified.

* If a builtin IO such as Position occurs in an arrayed struct, for example as an input to a GS,
  the array reference is moved to the split-off loose variable, which is given the array dimension
  itself.

When passing things around inside the shader, such as over a function call, the the original type
is used in a sanitized form that removes the builtIn qualifications and makes them temporaries.
This means internal function calls do not have to change.  However, the type when returned from
the shader will be member-wise copied from the internal sanitized one to the external type.
The sanitized type is used in variable declarations.

When copying split types and unsplit, if a sub-struct contains only user variables, it is copied
as a single entity to avoid more AST verbosity.

Above strategy arrived at with talks with @johnkslang.

This is a big complex change.  I'm inclined to leave it as a WIP until it can get some exposure to
real world cases.

Modify shader ballot extension by adding OpSubgroupReadInvocationKHR

Add support for SPV_NV_geometry_shader_passthrough

Fix a large number of Clang warnings about inconsistent usage of 'override'

Also, eliminate the 'atom' field of TPpToken.

Parsing a real 300 line shader, through to making the AST, is about 10% faster.

Memory is slightly reduced (< 1%).

The whole google-test suite, inclusive of all testing overhead, SPIR-V generation,
etc., runs 3% faster.

Since this is a code *simplification* that leads to perf. improvement, I'm not
going to invest too much more in measuring the perf. than this. The PP code is
simply now in a better state to see how to further rationalize/improve it.

Always keep 'token' outside.
Always return the string to upper levels inside.

CMake: Add option to make it possible to not build the executables

Add support for SPV_NV_sample_mask_override_coverage

Removed the preprocesser memory pool.

Removed extra copies and unnecessary allocations of objects related to the ones
that were using the pool.

Replaced some allocated pointers with objects instead, generally using more
modern techiques. There end up being fewer memory allocations/deletions to get right.

Overall combined effect of all changes is to use slightly less memory and
run slightly faster (< 1% for both, but noticable).

As part of simplifying the code base, this change makes it easier to see
PP symbol tracking, which I suspect has an even bigger run-time simplification
to make.

Also, checking both 'atom' and 'name' is redundant, and I'm hoping to
eliminate more atom stuff.