HLSL: implement 4 (of 6) structuredbuffer types

This is a partial implemention of structurebuffers supporting:

* structured buffer types of:
*   StructuredBuffer
*   RWStructuredBuffer
*   ByteAddressBuffer
*   RWByteAddressBuffer

* Atomic operations on RWByteAddressBuffer

* Load/Load[234], Store/Store[234], GetDimensions methods (where allowed by type)

* globallycoherent flag

But NOT yet supporting:

* AppendStructuredBuffer / ConsumeStructuredBuffer types
* IncrementCounter/DecrementCounter methods

Please note: the stride returned by GetDimensions is as calculated by glslang for std430,
and may not match other environments in all cases.

hlsl/hlslTokens.h

@@ -65,6 +65,7 @@ enum EHlslTokenClass {
     EHTokOut,
     EHTokInOut,
     EHTokLayout,
+    EHTokGloballyCoherent,
 
     // primitive types
     EHTokPoint,
@@ -256,6 +257,14 @@ enum EHlslTokenClass {
     EHTokRWTexture3d,
     EHTokRWBuffer,
 
+    // Structure buffer variants
+    EHTokAppendStructuredBuffer,
+    EHTokByteAddressBuffer,
+    EHTokConsumeStructuredBuffer,
+    EHTokRWByteAddressBuffer,
+    EHTokRWStructuredBuffer,
+    EHTokStructuredBuffer,
+
     // variable, user type, ...
     EHTokIdentifier,
     EHTokTypeName,