Only install platform packages if they're not already installed
Only install platform packages if they're not already installed

darcs-hash:20090730053430-adfee-fc178dfb851a34061d3f63debbadd937f96405bf.gz

gbaz/haskell-platform,erantapaa/haskell-platform,ardumont/haskell-platform,gbaz/haskell-platform,erantapaa/haskell-platform,erantapaa/haskell-platform,bgamari/haskell-platform,bgamari/haskell-platform,ardumont/haskell-platform,thomie/haskell-platform