SPV compression: Final check-in enabling this on MSVC 2012.  All compression submissions from Steve (spvremapper@lunarg.com).

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@31236 e7fa87d3-cd2b-0410-9028-fcbf551c1848