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/conditionalDiscard.frag.out

@@ -12,10 +12,11 @@
 0:10        Condition
 0:10        Compare Equal (bool)
 0:10          'v' (4-component vector of float)
-0:10          0.100000
-0:10          0.200000
-0:10          0.300000
-0:10          0.400000
+0:10          Constant:
+0:10            0.100000
+0:10            0.200000
+0:10            0.300000
+0:10            0.400000
 0:10        true case
 0:11        Branch: Kill
 0:13      move second child to first child (4-component vector of float)