Add precision qualifier propagation for swizzling, texture lookups, built-in funtions mapped to operators, comma op, and more robustly propagate for all binary/unary ops.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@21622 e7fa87d3-cd2b-0410-9028-fcbf551c1848