Call function synchronously when timeout is set to zero

[orslumen]

Well, this is more of an enhancement request than a bug.

I am running my integration tests asynchronously. Next to that I make sure that (most) calls to setTimeout use a timeout of 0 (zero) during the integration tests, to perform well.

But timer.js by default adds all timers and intervals to the queue, regardless of the timeout value.

I would like setTimeout to synchronously call the given function when the timeout is set to zero, see e.g. orslumen@fe499c2