[Haskell] Ann: Yogurt-0.3

Dear Haskellers,

I'm pleased to announce the release of Yogurt-0.3!

This version improves over 0.2 in several ways:

* It compiles and runs with GHC 6.10.
* The Mud monad is now built on top of IO.
* Vars are expressed as IORefs. No more unsafeCoerce needed.
* Forking of threads is supported, with callback into the Mud monad:
   > type RunMud = forall a. Mud a -> IO a
   > forkWithCallback :: (RunMud -> IO ()) -> Mud ThreadId
* Timers are no longer a primitive: they can be expressed as function of
forkWithCallback.
* Refactorings in the architecture: the features are a strict superset
of the previous version while the number of lines of code has decreased
by 10%.

All feedback is appreciated!

Thanks to Saizan on #haskell for helping me work around the predicative
types. :-)

The code is available at Google: http://code.google.com/p/yogurt-mud/

Kind regards,

Martijn.