glslang and SPIR-V: Some basic turn on for doubles (previously untested but existed code).  Partly from a submission, partly addressing bug 13772.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@30794 e7fa87d3-cd2b-0410-9028-fcbf551c1848