When pressing a button with the mouse and then moving the focus away,
the internal and visual state of the button would get updated, but the
released signal would not be emitted.
The same goes for disabling the button, although in 99% of the cases,
disabling the button will also move the focus, so the first case
already takes care of emitting the signal.
Task-number: QTBUG-42775
Change-Id: Ib6ba8e0a75f0349b66d1e799b02bd8498db85022
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@theqtcompany.com>