patch applied (ghc): Add more functionality to Digraph and refactor it's interface somewhat, including adding a Graph ADT

[Ian Lynagh]

Wed Jul 30 18:23:53 PDT 2008  Max Bolingbroke <batterseapower at hotmail.com>
  * Add more functionality to Digraph and refactor it's interface somewhat, including adding a Graph ADT

    M ./compiler/utils/Digraph.lhs -134 +296

View patch online:
http://darcs.haskell.org/ghc/_darcs/patches/20080731012353-9b787-2f005652444148283d8bb1a72c8dc2d783f89757.gz