PL/pgSQL RETURN NEXT was leaking converted tuples, causing

out of memory when looping through large numbers of rows.
Flag the converted tuples to be freed. Complaint and patch
by Joe.

src/pl/plpgsql/src/pl_exec.c

@@ -2472,6 +2472,7 @@ exec_stmt_return_next(PLpgSQL_execstate *estate,
 					{
 						tuple = do_convert_tuple(tuple, tupmap);
 						free_conversion_map(tupmap);
+						free_tuple = true;
 					}
 				}
 				break;