Updated the includer interface to allow relative includes.

This plumbs both the current file path and the include depth
back up to the includer. This allows the includer to properly
support relative paths.

This also replaces the string copy that was done during include
with a zero-copy method of accomplishing the same thing. This
prevents extra copies of entire files.

Much about const or temp is mechanical, about actual declaration,
while much is semantic, about something higher level.  This commit
checks every use everywhere, and for the high-level ones, substitutes
an encapsulated version instead.

Parser: Type promotion for operator modulus(%) is missing.

Support Linux-to-Windows cross compile via MinGW

Change-Id: Ie52f0b1b2b20948c6f4b3cb5474537d36a5a3385

SPV: Implement boolean selection for mix().

Use OpSelect to implement boolean selection of mix(). FMix is applicable
to linear blending of mix().

SPV test: Test dead-decoration removal.

SPV: Remove decoration of undefined IDs

Preprocessor: Fix array out of bounds bug in processing if-else-endif macros.

Fix issue #185 by removing OpDecorate instructions whose target IDs are
defined in unreachable blocks and thus not dumped in the generated
SPIR-V code.

If we are not inside an if macro, we cannot simply decrease
elsetracker.

Fixes https://github.com/KhronosGroup/glslang/issues/29.

SPV: Declare MultiViewport capability.

Fix issue #191:
https://github.com/KhronosGroup/glslang/issues/191

SPV: Add support for memory qualifiers.

SPV: Support the new OpCode - OpImageSparseRead

Remove bison binary

SPV: Continue to fix the issue of bool -> uint32

Fix line endings in Test/100.conf

For short-circuit operator (&& and ||), the conversion is missing.

SPV: Fix an issue caused by bool-to-uint32 conversion.

Fix compilation issues with MSVC 2010