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.

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()

This fixes compilation in build environments with stricter warnings enabled

The gl_in array has a special path due to context-specific
gl_MaxPatchVertices, making the code out of order for tagging built-ins.
This commit moves the tagging to the correct location.
This also fixes issue #80.

Expand to full isConstant() implementation.
Fix disassembler to generate texture look-up masks.

Generate correct image operand mask for Offset and ConstOffset(#77) and correct arg # for rect. texelFetchOffset.

This fixes a bug where a token that could be a keyword in one version
is not a keyword in another version, but treated like a non-member after
a "." dereference.

4 components are needed when used a texture, but not an image, which multiplies
layers and faces into the same coordinate.  This fixes it from using 4 everywhere,
to only using 4 for textures and 3 for images.