haskell-ghc-mod: re-enable the test suite
haskell-ghc-mod: don't rely on /bin/sh
haskell-ghc-mod: keep the original 'ghc-mod' binary in $out/bin, not $out
haskell-quickcheck-io: revert hard-coding of HUnit and QuickCheck versions

That patch broke the build on modern platforms. Instead of hard-coding
those versions globally, we should do so on a per-platform basis in
haskell-defaults.nix.
haskell-quickcheck-io: override versions of HUnit and QuickCheck on older versions of Haskell Platform
haskell-mime-mail: update to version 0.4.3
haskell-LambdaHack: update to version 0.2.10.6
haskell-github: patch to fix build