Proposal: Move 'split' into a separate class in System.Random

[Thomas DuBuisson]

The "split" routine in the RandomGen seems to be a sore spot for some
people and is perceived to have few users (even as a percentage of
RandomGen users).  I propose:

1) Making a class "SplittableGen":

class SplittableGen g where
  split :: g -> (g, g)

2) (re)moving the "split" routine from the RandomGen class.

See ticket 4314 [1] for the patch.

Period of discussion: Till October 8 (3.5 weeks, ending just over 1
week after ICFP)

Cheers,
Thomas

[1] http://hackage.haskell.org/trac/ghc/ticket/4314