[Deskbar] I'm working on an AsyncHandler

[Mikkel Kamstrup Erlandsen <kamstrup daimi au dk>]

Just notifying the list of what I'm currently doing. I've sketched out
an implementation of an AsyncHandler and are about to start implementing
it.

Basically the AsyncHandler is a special handler class running .query()
in it's own thread. This means that Matches will be returned
asynchronously. I've put great effort into ensuring that there will
never be no more than one thread per AsyncHandler.

Writing an async handler will be exactly like writing an ordinary
handler except that you will want to sprinkle check_query_changed()
around in your query() method.

I'll return later today with a prototype. Cheers,

Mikkel