WIP: HLSL: Add GS support

This PR adds:

[maxvertexcount(n)] attributes

point/line/triangle/lineadj/triangleadj qualifiers

PointStream/LineStream/TriangleStream templatized types

Append method on above template types

RestartStrip method on above template types.

glslang/Include/intermediate.h

@@ -621,6 +621,10 @@ enum TOperator {
     EOpMethodGatherCmpGreen,             // ...
     EOpMethodGatherCmpBlue,              // ...
     EOpMethodGatherCmpAlpha,             // ...
+
+    // geometry methods
+    EOpMethodAppend,                     // Geometry shader methods
+    EOpMethodRestartStrip,               // ...
 };
 
 class TIntermTraverser;