patch applied (cabal): Make contents of SrcDist more useful to outside users.

[Duncan Coutts]

Sat Apr 14 23:09:16 PDT 2007  Bryan O'Sullivan <bos at serpentine.com>
  * Make contents of SrcDist more useful to outside users.
  
  This change simply splits sdist into three functions.
  
  The normal sdist function remains unchanged from the caller's
  perspective, but it now consists of two phases, each an exported function.
  The source tree is prepared by prepareTree, and the archive is created
  by createArchive.
  
  This lets the cabal-rpm tool prepare a source tree and insert a few
  extra files into it before generating a tarball.
  

    M ./Distribution/Simple/SrcDist.hs -14 +54