HLSL: Refactor attribute implementation.

- make it sharable with GLSL
- correct the case insensitivity
- remove the map; queries are not needed, all entries need processing
- make it easier to build bottom up (will help GLSL parsing)
- support semantic checking and reporting
- allow front-end dependent semantics and attribute name mapping

glslang/Include/ConstantUnion.h

@@ -37,6 +37,9 @@
 #ifndef _CONSTANT_UNION_INCLUDED_
 #define _CONSTANT_UNION_INCLUDED_
 
+#include "../Include/Common.h"
+#include "../Include/BaseTypes.h"
+
 namespace glslang {
 
 class TConstUnion {