Change infrastructure to support constant folding across built-in functions, as required by 1.2 semantics. Partially fleshed out with min/max and some trig functions. Still have to complete all operations.
git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@20806 e7fa87d3-cd2b-0410-9028-fcbf551c1848
