Fix connections in libdbusmenu-qt
Connecting in Qt DBus has an additional check that parameters match. This requires introspecting the QMetaSlot to understand parameters. This requires the types to be registered.
This is independent of registering the DBus type for demarshalling.
Result was an error: QDBusAbstractInterface::connectNotify|QObjectPrivate::connectImpl Could not connect "com.canonical.dbusmenu" to "ItemsPropertiesUpdated"
Presumably this is the result of a Qt change as it worked at some point before, but I think it's a valid change?