patch applied (cabal-install): Add new InstallPlan type

[Duncan Coutts]

Mon Apr 14 10:19:14 PDT 2008  Duncan Coutts <duncan at haskell.org>
  * Add new InstallPlan type
  This is joint work with Kolmodin.
  An InstallPlan records what we want to install and records the outcome
  of installing packages. It has a fairly strict internal invariant which
  should guarantee that each package can be configured sucessfully.

    A ./Hackage/InstallPlan.hs

View patch online:
http://darcs.haskell.org/cabal-install/_darcs/patches/20080414171914-adfee-aaa7e78f45182814c57eba21863cb1505579767a.gz