Proposal: remove datatype contexts from base

The Haskell' committee decided to remove datatype contexts from the language: http://www.haskell.org/pipermail/haskell-prime/2011-January/003335.html (though this doesn't seem to be in the Report yet.) In the base package there are 4 of these: Data/Complex.hs:data (RealFloat a) => Complex a GHC/Arr.lhs:data Ix i => Array i e GHC/Real.lhs:data (Integral a) => Ratio a = !a :% !a deriving (Eq) Control/Arrow.hs:newtype ArrowApply a => ArrowMonad a b = ArrowMonad (a () b) As far as I know, removing them won't break any code that compiles now, so let's do it.