doc fix from Remi Turk
MERGE to STABLE
-- @'mfix' ('return' . h) = 'return' ('fix' h)@
--
-- [/left shrinking/ (or /tightening/)]
--- @'mfix' (\\x -> a >>= \\y -> f x y) = \\y -> 'mfix' (\\x -> f x y)@
+-- @'mfix' (\\x -> a >>= \\y -> f x y) = a >>= \\y -> 'mfix' (\\x -> f x y)@
--
-- [/sliding/]
-- @'mfix' ('Control.Monad.liftM' h . f) = 'Control.Monad.liftM' h ('mfix' (f . h))@,