patch applied (cabal): Move PackageDescription unit tests into a dedicated module

[Duncan Coutts]

Mon Feb  4 14:10:28 PST 2008  Duncan Coutts <duncan at haskell.org>
  * Move PackageDescription unit tests into a dedicated module
  and make the unit test module build again.
  The PackageDescription module no longer needs CPP.

    M ./Distribution/PackageDescription.hs -372
    M ./Makefile -5 +5
    M ./tests/ModuleTest.hs -42 +19
    A ./tests/PackageDescriptionTests.hs