patch applied (cabal-install): Added upgrade command

[Isaac Jones]

Mon Dec 31 13:39:53 PST 2007  ijones at syntaxpolice.org
  * Added upgrade command
  cabal upgrade installs the latest version of any currently installed
  package.
  

    M ./Hackage/Dependency.hs -2 +59
    M ./Hackage/Setup.hs +9
    A ./Hackage/Upgrade.hs
    M ./Main.hs +10
    M ./cabal-install.cabal +3