Added can_cast_type implementation for code_typet

Author: NathanJPhillips

src/util/std_types.h

@@ -999,6 +999,13 @@ inline code_typet &to_code_type(typet &type)
   return static_cast<code_typet &>(type);
 }
 
+template <>
+inline bool can_cast_type<code_typet>(const typet &type)
+{
+  return type.id() == ID_code;
+}
+
+
 /*! \brief arrays with given size
 */
 class array_typet:public type_with_subtypet