Comparison of function PMFs to virtual functions is flawed in QObject::disconnect

Take the following excerpt:

    QVERIFY(QObject::connect(&sender, &SenderObject::signal1, &o, public_slot));

    // disconnect the *private* virtual
    QVERIFY(!QObjectPrivate::disconnect(&sender, &SenderObject::signal1, o.d_func(), private_slot));

It's possible that the disconnect of the private will disconnect the public because public_slot and private_slot may have the same representation if they're both pointers to virtual member functions.

Testcase patch attached, currently produces:

FAIL!  : tst_QObject::disconnectPrivateVirtualSlots() '!QObjectPrivate::disconnect(&sender, &SenderObject::signal1, o.d_func(), private_slot)' returned FALSE. ()