patch applied (ghc): Print the right usage message

[Ian Lynagh]

Mon Jul  2 03:26:51 PDT 2007  Ian Lynagh <igloo at earth.li>
  * Print the right usage message
  The logic for printing the ghc and ghci usage messages was inverted.
  However, the ghci case will never actually happen with the current code,
  as we print a usage message when cli_mode == ShowUsage and choose the
  ghci usage message if cli_mode == DoInteractive. This should be fixed
  as part of a larger options handling overhaul.

    M ./compiler/main/Main.hs -2 +2