Improve error handling when using OLD_VALUE as alias name

13.0.0-dbg>CREATE OR REPLACE TABLE t3(a INT);

Query OK, 0 rows affected (0.018 sec)

13.0.0-dbg>INSERT INTO t3 VALUES (1);

Query OK, 1 row affected (0.002 sec)

13.0.0-dbg>UPDATE t3 SET a = 10 RETURNING OLD_VALUE(a) AS old_value;

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'old_value' at line 1

13.0.0-dbg>

13.0.0-dbg>UPDATE t3 SET a = 10 RETURNING OLD_VALUE(a) AS old_val;

+---------+

| old_val |

+---------+

|       1 |

+---------+

1 row in set (0.003 sec)

13.0.0-dbg>