WIP: HLSL: add ability to pass struct buffers with counters to fns

This modifies function parameter passing to pass the counter
buffer associated with a struct buffer to a function as a
hidden parameter.  Similarly function declarations will have
hidden parameters added to accept the associated counter buffers.

There is a limitation: if a SB type may or may not have an associated
counter, passing it as a function parameter will assume that it does, and
the counter will appear in the linkage whether or not there is a counter
method used on the object.

Test/hlsl.structbuffer.append.fn.frag

@@ -0,0 +1,23 @@
+
+// float4 Fn1(ConsumeStructuredBuffer<float4> arg_c)
+// {
+//     return arg_c.Consume();
+// }
+
+float4 Fn2(AppendStructuredBuffer<float4> arg_a, ConsumeStructuredBuffer<float4> arg_c)
+{
+    arg_a.Append(float4(1,2,3,4));
+    return arg_c.Consume();
+}
+
+AppendStructuredBuffer<float4>  sbuf_a;
+ConsumeStructuredBuffer<float4> sbuf_c;
+
+AppendStructuredBuffer<float4>  sbuf_unused;
+
+float4 main(uint pos : FOO) : SV_Target0
+{
+    // Fn1(sbuf_c);
+
+    return Fn2(sbuf_a, sbuf_c);
+}