recoco: Fix and document Scheduler.synchronized()
recoco: Fix and document Scheduler.synchronized()

This may have worked once upon a time, but it didn't today.
Fixed.  And documented, since it's useful but was totally
mysterious.

noxrepo/pox,MurphyMc/pox,MurphyMc/pox,MurphyMc/pox,noxrepo/pox,noxrepo/pox,MurphyMc/pox,MurphyMc/pox,noxrepo/pox