fix function used in mysql acceptance test for mysql 5.5

This was raised by @phe1129 (closes #180, supercedes #182).

When `binlog` is enabled and the `log_bin_trust_function_creators` system variable
is OFF (default=OFF), MySQL requires Create Function DDL to specify whether `DETERMINISTIC`,
`NO SQL`, or `READS SQL DATA` in its declaration. Otherwise the server gives exception.
For more details: http://dev.mysql.com/doc/refman/5.5/en/stored-programs-logging.html