Cleaning up the bug tracker

Cabal hackers, With 477 open issues, it's hard to use the bug tracker efficiently e.g. for prioritizing work. Gregory Collins and I have started cleaning up some dead bugs. We won't get through all of them, so I encourage other to join in a try to reproduce bugs and add a note to the bug if it's reproducible or not. Feel free to drop me an email if there are any bugs you think could be closed. -- Johan