Timeline for 2010.2 release

[Don Stewart]

http://trac.haskell.org/haskell-platform/wiki/ReleaseTimetable

We got held up on some blocking bugs in the 6.12.2 release, but now it
looks like 6.12.3 is due shortly.

I've revised the release timetable to take into account the 6.12.3 release.

Freeze expected start of June, with release to follow 2 weeks after.
That should last us through to November or so.

-- Don