PointerToMemberFunction support for QState::addTransition()

Qt5 having a new connection syntax which allows for the use of function pointers but QState::addTransiton doesn't support it yet.

It would be convenient (and consistent) to have function pointer syntax support for QState::addTransition() as well.

QFinalState *s2 = new QFinalState();
s1->addTransition(&button, &QPushButton::clicked, s2);