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/doWhileLoop.frag.out

@@ -11,7 +11,8 @@
 0:13        Compare Less Than (bool)
 0:13          direct index (float)
 0:13            'color' (4-component vector of float)
-0:13            0 (const int)
+0:13            Constant:
+0:13              0 (const int)
 0:13          'd' (uniform float)
 0:13        Loop Body
 0:12        Sequence