patch applied (cabal-install): Add a dependency graph to the InstallPlan

[Duncan Coutts]

Tue May  6 17:06:26 PDT 2008  Duncan Coutts <duncan at haskell.org>
  * Add a dependency graph to the InstallPlan
  Uses Data.Graph and annoyingly we also need to keep functions
  around for mapping between Graph.Vertex <-> PackageIdentifier

    M ./Hackage/InstallPlan.hs -4 +24

View patch online:
http://darcs.haskell.org/cabal-install/_darcs/patches/20080507000626-adfee-7bcffddcef60fbc53271cdf26eca110bf358f556.gz