Session tickets can be cached on the client side for hours (e.g.
graph.facebook.com: ~ 24 hours, api.twitter.com: 4 hours), because the
server does not need to maintain state.
We need public API for it so an application can cache the session (e.g.
to disk) and resume a session already with the 1st handshake, saving
one network round trip.
Task-number: QTBUG-20668
Change-Id: I10255932dcd528ee1231538cb72b52b97f9f4a3c
Reviewed-by: Richard J. Moore <rich@kde.org>