darcs patch: Stop pretending we might not have any Us... (and 3 more)

Hi Duncan, Patches for consideration. The first you have agreed to in the past, but I can't remember if you said it should go into the packages/Cabal repo or a repo for a release even further in the future. Thanks Ian Tue Apr 17 23:42:20 BST 2007 Ian Lynagh * Stop pretending we might not have any UserHooks Tue Apr 17 23:50:31 BST 2007 Ian Lynagh * Small tidyup Tue Apr 17 23:56:57 BST 2007 Ian Lynagh * Stop having hooks return an ExitCode that we then ignore Wed Apr 18 00:03:11 BST 2007 Ian Lynagh * Behave the same on Windows and non-Windows