Establish desktop completeness through version 1.50.  (gl_MaxVaryingFloats, implicit-cconversion safety, cube-sampler-array fix, add tests)

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@26253 e7fa87d3-cd2b-0410-9028-fcbf551c1848