WIP: HLSL: structuredbuffer counter functionality

This is WIP, heavy on the IP part.  There's not yet enough to use in real workloads.

Currently present:

* Creation of separate counter buffers for structured buffer types needing them.
* IncrementCounter / DecrementCounter methods
* Postprocess to remove unused counter buffers from linkage
* Associated counter buffers are given @count suffix (invalid as a user identifier)

Not yet present:

* reflection queries to obtain bindings for counter buffers
* Append/Consume buffers
* Ability to use SB references passed as fn parameters

glslang/Include/BaseTypes.h

@@ -223,6 +223,13 @@ enum TBuiltInVariable {
     EbvOutputPatch,
     EbvInputPatch,
 
+    // structbuffer types
+    EbvAppendConsume, // no need to differentiate append and consume
+    EbvRWStructuredBuffer,
+    EbvStructuredBuffer,
+    EbvByteAddressBuffer,
+    EbvRWByteAddressBuffer,
+
     EbvLast
 };