Enable the :toggle-threads command to work for workers which have Thread
capability. The implementation of that feature has the side effect that
the threading-enabled config option now sets the default view (threaded
or not threaded) for any worker, not just IMAP or notmuch.
Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>