Authors: Malcolm Wallace, Ross Paterson, Krasimir Angelov

  move createIfNotExists and removeFileRecursive functions from
  Distribution.Simple.Utils to System.Directory. The functions are renamed
  to createDirectoryIfMissing and removeDirectoryRecursive.

  avoid a few GHC warnings

  get IOError stuff from System.IO.Error instead of System.IO

  Minor tweaks to build with nhc98.

  OPTIONS pragma stuff for nhc98 and compat w/ ghc

  Use a custom monad ParseResult for parse results instead of Either PError,
  removing the need for Distribution.Compat.Error and the dependency on mtl.