patch applied (cabal-install): Have command line args override saved config not the other way around

[Duncan Coutts]

Tue Jan 15 12:02:58 PST 2008  Duncan Coutts <duncan at haskell.org>
  * Have command line args override saved config not the other way around
  Fixes setting the --prefix from the command line which was previously being
  ignored in favour of the default prefix from the config file.

    M ./Main.hs -4 +4