Remove some now-unecessary cleaning that causes problems for haskell-src
Remove some now-unecessary cleaning that causes problems for haskell-src

The code that removes .hs files in the source tree generated from .y files
had a comment:
    XXX: This is actually no longer necessary, but we keep it, so that
    clean works correctly on packages built with an older version of Cabal
This was causing problems for source distributions that include such
generated files (including haskell-src in extralibs).

20070920203257-3fd76-397803c26794ae89a0efd6609b70b59630be9525.gz

dcreager/cabal,dcreager/cabal