patch applied (packages/Cabal): Put _stub.{c|h} files under dist/ so they'll get cleaned. Fixes bug #154.

[Clemens Fruhwirth]

Mon Sep 17 05:30:42 PDT 2007  Duncan Coutts <duncan at haskell.org>
  * Put _stub.{c|h} files under dist/ so they'll get cleaned. Fixes bug #154.
  Only used with ghc-6.6 and later which supports the -stubdir flag.
  With earlier ghc versions the files still end up in the src dirs and so do not
  get cleaned.

    M ./Distribution/Simple/GHC.hs +2