While a plain lambda callback lacks a lot of the features of a real
Qt signal/slot connection, there are plenty situations where the
plain callback is all that's needed. Have some benchmark for more
educated guesses on timings.
Change-Id: I0c1fdfd2fd352d75c2af66fd713806bf3dd2d135
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
