[Interest] Logging meta call events

[Bernhard]

> Meta call events only happen for queued slot deliveries. For direct
deliveries,
> there's no event, so notify() will not be called. For those, you need to
use the
> hooks that QSignalSpy uses.

Well, since our state engines are completely driven by queued connections or
events this would be no problem.

I did some tests with QMetaCallEvent before writing my post to the list. And
the code kind of worked. However I have a bad feeling about using private
classes of Qt. It could break my code easily without me noticing it. 
Also I found a problem I could not solve properly... it happened that the
sender of the event had been deleted when the QMetaCallEvent arrived at the
receiver and the code crashed in that case when accessing
QMetaCall::sender() due to a dangling pointer.

P.S. Do you think my issue is reasonable in a way that I should write a
tracker suggestion asking for a public API?

-- 
Kind Regards
Bernhard Lindner