patch applied (cabal): add a Build-Type field, and use it in setupWrapper

[Ross Paterson]

Thu Jan 11 15:30:18 PST 2007  Ross Paterson <ross at soi.city.ac.uk>
  * add a Build-Type field, and use it in setupWrapper
  
  As discussed on the libraries list (Nov 2006), add a field Build-Type
  which can be used to declare that this package uses one of the boilerplate
  setup scripts.  This allows setupWrapper (used by cabal-setup and
  cabal-install) to bypass the setup script in this case and perform
  the setup actions itself.

    M ./Distribution/PackageDescription.hs -2 +20
    M ./Distribution/ParseUtils.hs -1 +5
    M ./Distribution/SetupWrapper.hs -18 +28
    M ./doc/Cabal.xml -3 +22