Add support for QObject::disconnect() non-member function pointers

when you connect a signal to a slot that is a static function, you can do something like this:

connect(pointertosender, &SenderType::signal, &ReceivingClass::staticslot);

so you would expect that to disconnect that connection, you would use

disconnect(pointertosender, &SenderType::signal, &ReceivingClass::staticslot);

but that does not work because 

no matching function for call to 'disconnect'

is it that when allowing for connecting static slots in the upgrade to Qt 5, you forgot to add support for disconnecting the connections?