HLSL: Build IO types bottom up, as parsed, and cache the original (IO).

Previously, this was done recursively, per object, and the nonIO version
was cached. This reverses both those approaches.

hlsl/hlslGrammar.cpp

@@ -1708,14 +1708,7 @@ bool HlslGrammar::acceptStruct(TType& type)
         new(&type) TType(typeList, structName, postDeclQualifier); // sets EbtBlock
     }
 
-    // If it was named, which means the type can be reused later, add
-    // it to the symbol table.  (Unless it's a block, in which
-    // case the name is not a type.)
-    if (type.getBasicType() != EbtBlock && structName.size() > 0) {
-        TVariable* userTypeDef = new TVariable(&structName, type, true);
-        if (! parseContext.symbolTable.insert(*userTypeDef))
-            parseContext.error(token.loc, "redefinition", structName.c_str(), "struct");
-    }
+    parseContext.declareStruct(token.loc, structName, type);
 
     return true;
 }