Log Message:
Update to version 5.0.21.

Full listing of changes:

http://dev.mysql.com/doc/refman/5.0/en/news-5-0-21.html

Notable changes include:
 - Security enhancement: Added the global max_prepared_stmt_count system
   variable to limit the total number of prepared statements in the
   server.
 - The default for the innodb_thread_concurrency system variable was
   changed to 8.
 - Fixes for CVE-2006-1516, CVE-2006-1517 and CVE-2006-1518.

 And a lot of bug fixes.