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/intermediate.h

@@ -633,6 +633,10 @@ enum TOperator {
     EOpMethodStore2,                     // ...
     EOpMethodStore3,                     // ...
     EOpMethodStore4,                     // ...
+    EOpMethodIncrementCounter,           // ...
+    EOpMethodDecrementCounter,           // ...
+    // EOpMethodAppend is defined for geo shaders below
+    EOpMethodConsume,
 
     // SM5 texture methods
     EOpMethodGatherRed,                  // These are covered under the above EOpMethodSample comment about