PHP 5.3 mysqlnd requires new-style passwords

[geofft]

The sql.mit.edu servers currently have old_passwords=1 set in the mysqld configuration for compatibility with MySQL 3.x and 4.x clients. The ​MySQL native driver in PHP 5.3 only knows how to deal with ​new-style passwords; this will probably bite us hard when we move to PHP 5.3 as part of upgrading to Fedora 13.

We'll need to either figure out if we can do the backward-compatible but insecure hack of making PHP clients able to use old-style passwords (disable the native driver? patch it?), or if we can drop support for MySQL clients that don't support new-style passwords, i.e., 4.x and below.