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

Test/hlsl.structbuffer.incdec.frag

@@ -0,0 +1,19 @@
+RWStructuredBuffer<uint4>      sbuf_rw_i;
+RWStructuredBuffer<uint4>      sbuf_rw_d;
+
+RWStructuredBuffer<uint4>      sbuf_rw_nocounter; // doesn't use inc or dec
+
+float4 main(uint pos : FOO) : SV_Target0
+{
+    uint4 result = 0;
+
+    sbuf_rw_i[7];
+    sbuf_rw_d[7];
+
+    sbuf_rw_nocounter[5] = 2;
+
+    uint c1 = sbuf_rw_i.IncrementCounter();
+    uint c2 = sbuf_rw_d.DecrementCounter();
+
+    return float4(result.x, result.y, c1, c2);
+}