#3260: Update MySQL to 5.0.51a

VDT 1.8.1 currently ships with MySQL 5.0.41. Since that time there have
been three updates: 5.0.45, 5.0.51, and 5.0.51a. Each one of these
contains security fixes. It's very hard to tell if they affect the VDT
or not. I think we should be conservative and assume they need to be
fixed. Therefore we should upgrade MySQL to 5.0.51a.

I would like to upgrade to 5.0.51a, but there wasn't a link to download
the 5.0.51a source code. I downloaded 5.0.51 from a mirror, edited the
URL, and got 5.0.51a. If we think we can trust this download, we should
use it. Otherwise we'll use 5.0.51. I suspect we can trust it.

http://mirror.x10.com/mirror/mysql/Downloads/MySQL-5.0/mysql-5.0.51a.tar.gz