event based timer

[Piotr Szturmaj]

Martin Nowak wrote:
> You are aware though that in your timer, the callback is executed from
> within a different thread.

Yes. User should be aware of this different thread and should perform 
synchronization manually. Anyway, it is possible to relay callbacks to a 
queue and then one can wait for events on that queue.
(This timer class was designed to handle thousands of concurrent timers.)