QTimeZone::hasTransisions() may be misleading

It's documented to report whether the system zone backend supports looking up transitions.
However, QTimeZone's instantiation can use a QUtcTimeZonePrivate backend, whose hasTransitions(), inherited from QTimeZonePrivate, returns false.
So the actual implementation of QTimeZone::hasTransitions() reports on whether the instance it's called on uses a backend that supports transitions.
That's a documentation issue.

Meanwhile, for anyone who hasn't read the documentation, the name hasTransitions() might reasonably lead folk to suppose it's a test of whether the zone itself has any transitions, as well as its backend supporting them. We could perhaps add a zoneHasTransitions() method to fill that niche.