patch applied (ghc): Use update-alternatives for handling generic tool names

[Sven Panne]

While we are at the topic: Is there a deep reason why the cpphs repo is on 
www.cs.york.ac.uk and not on darcs.haskell.org? I would like to add a .spec 
file etc. to make it a standalone tool, but I can't commit currently. :-(

BTW, the toplevel directory of darcs.haskell.org needs some serious cleanup, 
there are packages, scripts, different versions of the same thing, papers, 
etc. all lying around in a rather unstructured way... :-P Even if cleaning up 
things would mean changing some repo URLs, doing this now will be less 
painful than later. Currently, things look a little bit CP/M-like (no support 
for subdirectories, for the younger amongst us ;-).

Cheers,
    S.