Data.* collections maintenance

[Jean-Philippe Bernardy]

Hello,

As some demand seem to exist for the job, I volunteer to take
over/resume maintenance of Data.Map and friends. In the hope that will
alleviate the heavy load on the compiler maintainers :)


Pending issues include :
  - Better integration of Map and Set (proposed by John Meacham)
  - More performance tests and QuickCheck properties (Christian Maeder)
  - Monoid instances (is this still current ?)

Surely I have missed something, please state your unaddressed bug
reports and wish list items.

Cheers,
JP.