Add strict fmap

Add a strict version of fmap to the standard libraries.

infixl 4 <$!>
  
(<$!>) :: Monad m => (a -> b) -> m a -> m b
f <$!> m = do x <- m
              return $! f x
{-# INLINE (<$!>) #-}

Libraries discussions:

Take 1: http://www.haskell.org/pipermail/libraries/2013-November/021728.html Take 3: http://www.haskell.org/pipermail/libraries/2014-April/022864.html

Trac metadata

Trac field	Value
Version	7.8.2
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	None
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