(zone): Init `line-spacing' from orig buffer.

(zone): Init `line-spacing' from orig buffer.
(zone-replace-char): Take `count' and `del-count'
instead of `direction'.  Update callers.  When `del-count' is
non-nil, delete that many characters, otherwise `count' characters
backwards.  Insert the newly-replaced string `count' times.
(zone-fret): Handle chars w/ width greater than one.
(zone-fall-through-ws): No longer take window width `ww'.
Update callers.  Add handling for `char-width' greater than one.
(zone-pgm-drip): Update var holding window-end position every cycle.