Changes right alt key with a control key on a macbook keyboard.

I'm using this on 10.6 added with lingon as a user daemon. Add the provided plist as a User Daemon with lingon or however those launchd things are added.

Bugs:
  - With some versions I used to get a bunch of gray screens when plugging/unplugging an external keyboard (back on 10.5). I don't have an external keyboard now so I have no clue if this still happens.
  - Sometimes it just stops working, no clue why. It generally comes back to life after a while.