minor library changes

This should be a list of minor (mostly) backwards compatable changes to the standard libraries. Proposed new libraries should go on NewLibraryCandidates

• signatures of when and unless generalized
• move 'join' and 'ap' into the Monad class
• remove exports of functions from libraries that are also exported by the prelude (to make overriding prelude functions easier)
• lookup,elemIndex,find,findIndex to be generalized to return result in monad instead of forced to be a maybe
• remove catch from the Prelude
• behavior of array on repeated indices (H98: bottom, GHC: last value)
• read of octal and hex Int constants ( email message)
• swap for tuples
• specify strictness of I/O functions ( thread on haskell list)
• make groupBy (and possibly nubBy) work with any relation, not just symmetric transitive ones ( message on haskell-cafe)

new simple functions

replicateM, replicateM_, repeatM, repeatM_

-- | the generalization of readIO. readIO can be deprecated if wished if this is included.
readM :: (Read a, Monad m) => String -> m a
readM = ... 

toMaybe :: Bool → a → Maybe a (added to Maybe library)