patch applied (cabal-branches/cabal-1.2): Export PreProcessor constructor and mkSimplePreProcessor

[Ian Lynagh]

Fri Nov 16 06:53:27 PST 2007  Duncan Coutts <duncan at haskell.org>
  * Export PreProcessor constructor and mkSimplePreProcessor
  Otherwise it is impossible to declare new pre-processors in Setup.hs files

    M ./Distribution/Simple/PreProcess.hs -2 +2