(ispell): Deactivate mark before the Ispell run.

(ispell): Deactivate mark before the Ispell run.
(ispell-point): Delete the sit-for; it was confusing.
(ispell): Don't use save-excursion; just restore current buffer.
(ispell-next): Don't save-excursion or save-window-excursion.
(ispell-point): Don't save-excursion.
(ispell-window-configuration): New variable.
(ispell-show-choices): Set it if not nil.
(ispell-next): Initialize to nil.  Restore at end.