HLSL: allow length() on scalars

Covers if(cond), while(cond), do-while(cond), for(;cond;), and (cond ? :).
Fixes #778.

Unknown how extensive the semantics need to be yet. Need real
feedback from workloads. This is just done as part of unifying it
with the class/struct namespaces and grammar productions.

HLSL: Fix an issue of frexp().

Don't emit NV-specific interface members if NV extensions are disabled.

The "exp" parameter is floating-point type in HLSL intrinsic while it is
integer type in GLSL built-in function.

HLSL: fix crash on empty struct return from entry point

This allows global initializers to use $Global members.

Thanks to @steve-lunarg for his input and discussions on handling member functions.

Another precurser to getting member non-static functions working.

HLSL: use prefix for builtin functions names to avoid namespace colli…

HLSL: Buffer types should be unsampled.

It would have been possible for globally scoped user functions to collide
with builtin method names.  This adds a prefix to avoid polluting the
namespace.

Ideally this would be an invalid character to use in user identifiers, but
as that requires changing the scanner, for the moment it's an unlikely yet
valid prefix.

Still need: pass by reference in SPIR-V and symbol-table level
for accessing 'this' members from member functions.

Also use this to move deferred member-function-body parsing to a better
place.

This should also be well poised for implementing the 'namespace' keyword.

RWBuffer objects were generating (properly) unsampled resoures, while
Buffer objects were not.  This fixes that.

Adding a test for this also uncovered an extraneous \r in the runtests script,
fixed now.

SPV: Fix unexpected declarations of capability and extension

Fix building on MinGW-w64

Merge branch 'semantic_handling' of https://github.com/TiemoJung/glslang into TiemoJung-semantic_handling

Makes some white-space differences in most output, plus a few cases
where more could have been put out but was cut short by the previous
fix-sized buffer.