patch applied (cabal-install): Handle constraints on paired packages

[Duncan Coutts]

Sat Oct  4 22:19:19 PDT 2008  Duncan Coutts <duncan at haskell.org>
  * Handle constraints on paired packages
  The trick is that when applying constraints to paired
  packages, the constraint has to exclude both packages at
  once. We exclude the pair together or not at all. If it
  would only exclude one then we discard the constraint.

    M ./Distribution/Client/Dependency/TopDown/Constraints.hs -2 +9

View patch online:
http://darcs.haskell.org/cabal-install/_darcs/patches/20081005051919-adfee-e7c46552c20c802339eef1055c41fcbded570e46.gz