darcs patch: Split known-extensions off into their own type, and re...

1 patch for repository http://darcs.haskell.org/packages/Cabal: Tue Oct 26 00:26:24 BST 2010 Ian Lynagh * Split known-extensions off into their own type, and remove knownExtensions The knownExtensions list had already got out of sync with the datatype. Now we use an Enum instance to get the list of constructors. Also, having the actual extensions in a separate type than UnknownExtension and EnableExtension makes it easier to add extension disabling support later.