Bug #28921 Queries containg UDF functions are cached

Additional edits to the 5.0 ChangeSet|1.2519 that are necessary for the fix to work with the new code structure in 5.1.

sql/item_create.cc

@@ -2437,6 +2437,7 @@ Create_udf_func::create(THD *thd, udf_func *udf, List<Item> *item_list)
     my_error(ER_NOT_SUPPORTED_YET, MYF(0), "UDF return type");
   }
   }
+  thd->lex->safe_to_cache_query= 0;
   return func;
 }
 #endif