Check for hexadecimal literals exceeding MaxTokenLength.

Nonfunctional: minor: use std::array for per-set shifts, fix warning.

Two unrelated, minor tweaks:

(1) Use std::array for shiftBindingForSet.  Now matches shiftBinding.
(2) Add parens in shouldFlatten() to make compiler warning happy.

Add per-descriptor-set IO mapping shift values.

This PR adds the ability to provide per-descriptor-set IO mapping shift
values.  If a particular binding does not land into a per-set value,
then it falls back to the prior behavior (global shifts per resource class).

Because there were already 6 copies of many different methods and internal
variables and functions, and this PR would have added 6 more, a new API is
introduced to cut down on replication and present a cleaner interface.
For the global (non-set-specific) API, the old entry points still exist
for backward compatibility, but are phrased internally in terms of the
following.

    // Resource type for IO resolver
    enum TResourceType {
        EResSampler,
        EResTexture,
        EResImage,
        EResUbo,
        EResSsbo,
        EResUav,
        EResCount
    };

Methods on TShader:

    void setShiftBinding(TResourceType res, unsigned int base);
    void setShiftBindingForSet(TResourceType res, unsigned int set, unsigned int base);

The first method replaces the 6 prior entry points of various spellings, which
exist now in depreciated form.  The second provides per-resource-set functionality.
Both accept an enum from the list above.

From the command line, the existing options can accept either a single shift value as
before, or a series of 1 or more [set offset] pairs.  Both can be provided, as in:

    ... --stb 20 --stb 2 25 3 30 ...

which will use the offset 20 for anything except descriptor set 2 (which uses 25) and
3 (which uses 30).

Desktop defaults to highp for samplers, but this should not apply to the built-in
functions, so make it appy only to user declarations.

Preprocessor: Evaluate INT_MIN / -1 to 0.

HLSL: Partially flatten hierarchies, instead of all or nothing.

  This division is undefined behaviour which raises SIGFPE on x86.
  Most C++ preprocessors evaluate this silently to 0.

GLSL: Don't try to swizzle void.

Also, rationalized this to generally make it safer and more readable.
It could use a more modern approach, at some point...

Fixes #1088.

Fixes #1092.  Allows arrays of opaques to keep arrayness, unless
needed by uniform array flattening.
Can handle assignments of mixed amounts of flattening.

HLSL: nonfunctional: add helper access methods to TAttributeMap

Set cmake-policy CMP0048 to NEW

HLSL: nonfunctional: rename setId -> switchId, add comment

Add getAsLoopNode() method for TIntermLoop

There was some code replication around getting string and integer
values out of an attribute map.  This adds new methods to the
TAttributeMap class to encapsulate some accessor details.

follow local conventions of spaces

Method rename, add comment about its intended use.  No
test diffs.

Fixes #1091.

Only track variables in the global scope

The semantics differ between GLSL/HLSL and SPIR-V.
Translate between these.