patch applied (cabal): Add a "cpp-options:" field and use it for pre-processing .hs .hsc .chs files

[Duncan Coutts]

Wed Oct 17 09:47:47 PDT 2007  Duncan Coutts <duncan at haskell.org>
  * Add a "cpp-options:" field and use it for pre-processing .hs .hsc .chs files
  This is for pre-processing Haskell modules, not for C code. We already have
  cc-options for that purpose. Up 'til now people have been abusing ghc-options
  for this purpose. Even Cabal itself was guilty of doing that.

    M ./Distribution/PackageDescription.hs +6
    M ./Distribution/Simple/GHC.hs +1
    M ./Distribution/Simple/PreProcess.hs -9 +6