[RP] altgr support

[shawn]

So I've added some support for altgr (as far as I can tell). Its on
the rel-0-1-0 branch. We plan to fix altgr and release 0.1.1. This is
why its on the 0.1.0 branch.

Try it out. There are still some problems: you can't use altgr in the
prefix key. altgr could get out of sync, if you hold down altgr as the
input window is being mapped altgr status will get out of sync. This
is because ratpoison has to keep track of altgr.

As I write this I have a better idea. But check it out and see if it
works for you. In the mean time *ahem* I'll fix it :)