patch applied (ghc): Add basic :edit support

[Simon Marlow]

Thu Sep 28 06:51:56 PDT 2006  Simon Marlow <simonmar at microsoft.com>
  * Add basic :edit support
  Without jumping to line numbers or %-expansion, we could add that later.

    M ./compiler/ghci/InteractiveUI.hs -2 +50
    M ./docs/users_guide/ghci.xml +15