It appears that you can update your mysql jdbc driver by replacing the one under the Openfire installation directory's lib/ directory. It's called "mysql.jar" right now... just back that up, download the latest from mysql's site, and copy it into that lib/ directory (making sure to call it the same name - mysql.jar).
I have attached the lastest MySQL JDBC Driver for convinience.. if you feel so inclinded to download your own... it's available at:
-- Make sure you rename this download jar to "mysql.jar" before dropping it into your openfire_installation/lib/ directory