darcs patch: Mark -XGenerics as deprecated (and 2 more)

3 patches for repository http://darcs.haskell.org/cabal: Thu May 26 10:13:23 CEST 2011 jpm@cs.uu.nl * Mark -XGenerics as deprecated Thu May 26 10:14:02 CEST 2011 jpm@cs.uu.nl * Add the -XDeriveGeneric extension Thu May 26 10:14:38 CEST 2011 jpm@cs.uu.nl * Add the -XDefaultSignatures extension