(highlight-changes-mode): Rename from

(highlight-changes-mode): Rename from
highlight-changes; no longer uses sub-modes active and
passive;  implemented by define-minor-mode.
(highlight-changes-toggle-visibility): New function, to replace
the old passive/active submodes of global-highlight-changes-mode;
implemented by define-minor-mode.
(global-highlight-changes-mode'): Rename from
global-highlight-changes; rewrite using define-globalized-minor-mode.
(hilit-chg-major-mode-hook, hilit-chg-check-global)
(hilit-chg-post-command-hook, hilit-chg-check-global)
(hilit-chg-update-all-buffers, hilit-chg-turn-off-maybe): Remove due
to use of define-globalized-minor-mode.
(highlight-changes-global-initial-state): Change to be boolean.
(highlight-changes-visible-string, highlight-changes-invisible-string):
Rename from highlight-changes-active-string and
highlight-changes-passive-string.
(hilit-chg-update, hilit-chg-set): Use them.
(global-highlight-changes-mode): Rename from global-highlight-changes.
(hilit-chg-map-changes, hilit-chg-display-changes): Add arguments to
docstring.
(hilit-chg-hide-changes): Rewrite to use dolist.
(hilit-chg-set-face-on-change, hilit-chg-update)
(highlight-changes-rotate-faces): Use highlight-changes-visible-mode
variable instead of testing highlight-changes-mode.
(highlight-markup-buffers): Add reuire ediff-util;  argument on calls
to highlight-changes-mode changed.
(highlight-compare-with-file): Fix problems with interactive
call giving invalid default file.