Implement write-only semantic checking, the non-r32f/i/u readonly/writeonly check, and ES 3.1 support of volatile.  Also, fix a typo in MaxComputeGroupY.


git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@27765 e7fa87d3-cd2b-0410-9028-fcbf551c1848