Add KProtocolInfo::workerHandlesNotify() to match new lingo
The feature slaveHandlesNotify was introduced in cf8906a4, with the only user the kio desktop file at that point. The KIO desktop slave though lost that bit accidentally during the conversion to JSON metadata in plasma/plasma-workspace!904 (merged). No other users known at this point.
Implemetation done without actual testing at this point, need yet to explore the desktop kio worker/slave.
Edited by Friedrich W. H. Kossebau