patch applied (cabal): Simplify default Setup.hs example

[Duncan Coutts]

Sat Jan 26 15:34:27 PST 2008  Duncan Coutts <duncan at haskell.org>
  * Simplify default Setup.hs example
  make it a .hs like everyone else uses

     ./DefaultSetup.lhs -> ./DefaultSetup.hs
    M ./DefaultSetup.hs -5 +3