patch applied (cabal-install): Make a proper RepoIndex ADT

[Duncan Coutts]

Thu Jan 17 09:58:54 PST 2008  Duncan Coutts <duncan at haskell.org>
  * Make a proper RepoIndex ADT
  This represents the collection of packages from a remote repo.
  It encodes the policies on how we find packages when we have multiple repos.
  The policy is encoded in the repo merge operation and in the various kinds of
  lookup functions.

    M ./Hackage/Dependency.hs -28 +28
    M ./Hackage/Index.hs -14 +191
    M ./Hackage/List.hs -3 +5
    M ./cabal-install.cabal -1 +2