Save the MySQL resource from dying!

## Problem

In the **Alternate Authentication** plugin (`alt_auth`), the `otherdb` authentication method is broken.  Because `otherdb` forms another MySQL resource to communicate with another database, the preexisting MySQL database resource for the local e107 installation would no longer be found by default parameters all throughout the system for the rest of the script's execution.

Any attempts to sign in properly print the `LAN_LOGIN_31` error, _Your credentials could not be added to the system_, and the local user table is not updated with the source user.

## Workaround

I bypassed the creation of another `mysql_connect()` by using PDO.  This is meant to be a quick and dirty fix.

## Solution

Overthrow the usage of the MySQL extension...

I'm seeing some progress in introducing PDO in `e107_handlers/mysql_class.php`, so... looks like that's already happening.