Tweak full refresh coutner logic

Don't increase it for regional updates
Try to avoid update_regions_func poisoning

Reset it at the end of repaint() even if nothing was found dirty
Try something w/ the FM nav buttons...

Papering over my puzzlement as to why the first setDirty calls doesn't
seem to take?
Try to avoid more update_regions_func mismatches
Oops.

Never switch to a FULL refresh for a regional update
Tweak previous commit.

Looks better this way. (ensure regional updates are always PARTIAL, in
case we get a region attached to an automatically triggered refresh, not
marked force_partial [which, hey, shouldn't happen, but apparently does
sometimes ^^])