There is a new additional StateChanged() signal coming from NetworkManager with additional reason property so
with that we can now check what was the reason for the changed state. Use this new signal when NM 1.8.0 is present
and emit also the old one for backward compatibility.
There is just one minor problem, with two stateChanged() signals you will need to specify to which signal you want
to connect to when using Qt5 syntax for signals/slots and without that you won't compile current code, i.e. of plasma-nm