patch applied (ghc): Support for adding custom commands to an individual breakpoint

[Simon Marlow]

Fri May 11 05:49:29 PDT 2007  Simon Marlow <simonmar at microsoft.com>
  * Support for adding custom commands to an individual breakpoint
  
    :set stop N <cmd>
  
  runs <cmd> when breakpoint N is hit.  Note that the command to run
  might be a macro (defined with :def), and the macro can invoke
  :continue, so it is now possible to do clever things like conditional
  breakpoints, or ignoring the next K hits of a breakpoint.

    M ./compiler/ghci/GhciMonad.hs -3 +11
    M ./compiler/ghci/InteractiveUI.hs -27 +58