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

Test/constErrors.frag

@@ -18,5 +18,5 @@ void main()
     vec4 e[constInt + uniformInt]; // error
     vec4 f[uniformInt + constInt]; // error
 
-    vec4 g[sin(3.2)];              // okay
+    vec4 g[int(sin(0.3)) + 1];     // okay
 }