darcs patch: Put pre-processed source into the dist/b... (and 2 more)

[Simon Marlow]

Duncan Coutts wrote:
> Those patches I was talking about. I'd apreciate a review :-)

Looks fine - although as we talked about on IRC, we should think carefully about 
what sdist is supposed to do, and the difference between Happy/Alex-generated 
.hs files and c2hs-generated .hs files.  The former should go in an sdist, but 
not the latter.

Cheers,
	Simon