Proposal: add Functor instance to Control.Exception.Handler

[Patrick Palka]

A Functor instance for Handler could be useful: e.g.

foo :: IO (Maybe a)
handlers :: [Handler ()]

foo `catches` map (Nothing <$) handlers

Proposed instance definition:

instance Functor Handler where
     fmap f (Handler h) = Handler (fmap f . h)

Deadline: 2 weeks