Add full support for uniforms with initializers, including intra-stage link validation of aggregate constant initializers.

This included 
 - encapsulating aggregate constants
 - removal of constant-aggregate comparison algorithms, instead using a flattened and direct std::vector comparison
 - adding structure type comparison for independently declared structures that still might match types



git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@23274 e7fa87d3-cd2b-0410-9028-fcbf551c1848

Test/baseResults/constErrors.frag.out

@@ -16,6 +16,7 @@ ERROR: node is still EOpNull!
 0:?     'inVar' (smooth in 4-component vector of float)
 0:?     'outVar' (out 4-component vector of float)
 0:?     'constInt' (const int)
+0:?       3 (const int)
 0:?     'uniformInt' (uniform int)
 0:?     's' (structure)
 0:?     's2' (structure)