Added RPM generation capability to Cabal

[Bryan O'Sullivan]

Duncan Coutts wrote:
> Great stuff Bryan, I look forward to seeing the patches. Do darcs send
> them to this list for review.

I'd be happy to, but my darcs repo contains about 50 patches that 
resulted from many incremental checkpoints as I went.  I'm guessing that 
you'd prefer to see something closer to three or four?

My darcs fu is not strong enough to know whether there's an easy way to 
do this, so I may end up having to diff my branch with the main 
repository and repatch.

	<b