concrete functor and monad transformers
#27Backport Num/Bits/IsString/etc. instances from base-4.9
duairc introduced these instances in http://git.haskell.org/ghc.git/commit/8b57cac5974c9fffccbcae3104b5b5d18760749e. This patch ( http://hub.darcs.net/RyanGlScott/transformers/patch/990b4ab02ff742296e6071337996330388e2cb62 ) backports them to transformers.
