Toggle Highlight-Changes mode in all buffers.
With prefix ARG, enable Global-Highlight-Changes mode if ARG is positive;
otherwise, disable it. If called from Lisp, enable the mode if
ARG is omitted or nil.
Highlight-Changes mode is enabled in all buffers where
`highlight-changes-mode-turn-on' would do it.
See `highlight-changes-mode' for more information on Highlight-Changes mode.
(fn &optional ARG)
Non-nil if Global-Highlight-Changes mode is enabled.
See the command `global-highlight-changes-mode' for a description of this minor mode.
Setting this variable directly does not take effect;
either customize it (see the info node `Easy Customization')
or call the function `global-highlight-changes-mode'.