SPV: Implement GLSL interpolation built-in functions.

Dealing with the 110 toolset seems not worth it.

Avoid read past end of operands vector for EOpFrexp

When emitting SPIR-V code for frexp, avoid access
beyond the end of the operands vector.  When constructing
the OpExtInst, construct a new arguments vector instead of
modifying the existing operands vector.  In the case of OpFrexp,
well need that last operand later on to generate the store.

Fixes https://github.com/KhronosGroup/glslang/issues/110

Change-Id: Ibc380fadf5e600ac491932e9ecef7afe2d72fd7f

SPV: Distinguish between std140 and std430 layouts, and correctly use alignments as the base for strides.

Scanner optimisations

In addUnaryMath, check for 'child' being null before dereferencing it.

Fail InitProcess() when InitThread() fails.

Fix ordered pointer comparison build warning/error

Use generic osinclude.h.

Using platform-neutral osinclude.h makes it easier to substitute
implementation when necessary and eliminates some variability between
build configurations.

Also, generally allow ES variable indexing of in/out blocks.

Handles the case of
    float[] x = float[] (1.0, 2.0, 3.0),
            y = float[] (1.0, 2.0, 3.0, 4.0);
where a shallow copy of the type arrayness from the left-most float[]
was getting used twice.

SPV: Fix an issue related with using CubeArrayShadow for texture()

Build: Use common osinclude.h header file that redirects per-platform, remove obsolete build files, enforce relative includes.

* Linux folder has been renamed to Unix, to match defines and so that it
  compiles on OS X.
* This removes the need for a per-platform include search path for the
  right OS folder

* This also moves bison generated files into the source tree, so that
  include of glslang_tab.cpp.h and includes from glslang_tab.cpp work
  the same way.

There is no calls to the TPpContext that could change the current input,
so every calls to pp->getChar and pp->ungetChar ultimately call this->getch
and this->ungetch while adding overhead of virtual calls and vector::back.

Remove obsolete unistd.h file

The presence of this file can cause build issues when integrating glslang
into other projects.

Various build fixes when using newer GCC versions with warnings enabled

Encountered with GCC-4.7.3 in a build environment where warnings are enabled
and treated as errors.

Replace sprintf() usage with snprintf()