C++: Strip away specifiers and typedefs when finding iterator parameters for a string taint function.

cpp/ql/lib/semmle/code/cpp/models/implementations/StdString.qll

@@ -66,7 +66,7 @@ abstract private class StdStringTaintFunction extends TaintFunction {
    * Gets the index of a parameter to this function that is an iterator.
    */
   final int getAnIteratorParameterIndex() {
-    this.getParameter(result).getType() instanceof Iterator
+    this.getParameter(result).getUnspecifiedType() instanceof Iterator
   }
 }