[racket] racket ppa for ubuntu

I have built a ppa for racket on Ubuntu. This is pretty alpha so let me
know if there are any issues with it (besides the one outlined below).

Information page: https://launchpad.net/~plt/+archive/racket

To install do:
$ sudo add-apt-repository ppa:plt/racket
(Use 'sudo apt-get install python-software-properties' if you dont have
add-apt-repository)
$ sudo apt-get update # not sure if this is really needed
$ sudo apt-get install -f racket
You need the -f because there is a conflict between `racket' and
`racket-common' about some HISTORY.txt file. I'll try to fix that for
the next release.

I made the ppa on a lucid (10.04) system and tested there. I'm not 100%
it will work on non-lucid systems but I guess it should. Right now there
are builds for i386 and amd64.