Proposal #2769: Export mapAccumR from Data.Map, Data.IntMap

[Matti Niemenmaa]

Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2769
Discussion period: 1 week

The `mapAccumR` function has been written in both the Data.Map and IntMap
sources but it's commented out and not exported. This seems to be an error and I
propose that it be simply uncommented.

The issue can be worked around by using Data.List.mapAccumL on the descending
list representation of the Map, but that's hardly optimal.

Seems like a no-brainer to me, hence the short discussion period.