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/versionsClean.vert.out

@@ -6,7 +6,8 @@
 0:42        'gl_Position' (gl_Position 4-component vector of float)
 0:42        Construct vec4 (4-component vector of float)
 0:42          'color' (in 3-component vector of float)
-0:42          142.000000
+0:42          Constant:
+0:42            142.000000
 0:?   Linker Objects
 0:?     'color' (in 3-component vector of float)
 0:?     'foo' (uniform sampler2DRect)