Oops, fixing the ghosts of bugs past. :-) Good thing I remembered how I

Oops, fixing the ghosts of bugs past. :-)  Good thing I remembered how I
fixed this when I made the mistake the first time.
The view code wasn't properly handling the transition across tile
boundaries so we'd get a 'flash' of the scene wrongly transformed for
one frame at every tile boundary crossing.  This is what
scenery.get_next_center() is for.