haskell-split: add version 0.1.4.3 for the benefit of GHC 6.x
haskell-defaults.nix: don't override 'Cabal' in GHC 6.10.4; it's a core library
haskell-async: fix build with GHC 6.12.x
haskell-scientific: add versions 0.1.0.1 and 0.3.2.1