patch applied (packages/Cabal): Improve style and performance of PackageIndex.dependencyClosure

[Ian Lynagh]

Tue May  6 16:44:47 PDT 2008  Duncan Coutts <duncan at haskell.org>
  * Improve style and performance of PackageIndex.dependencyClosure
  Keep the completed set as another PackageIndex rather than a list.
  We want to return an index at the end anyway and in the mean time
  we want to do lots of lookups to see if we've visited previously.

    M ./Distribution/Simple/PackageIndex.hs -12 +10

View patch online:
http://darcs.haskell.org/packages/Cabal/_darcs/patches/20080506234447-adfee-60242561c4f80aca290c1faa3b28819f681de819.gz