bug#11680: flyspell should use mouse-3 instead of mouse-2

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Sat, 2 Nov 2019 01:25:01 +0100
> Cc: l26wang@gmail.com, 11680@debbugs.gnu.org
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> > This would be a backward-incompatible change, so we cannot just change
> > it because someone asked for that.  I, for example, use that menu on
> > mouse-2 all the time.
> 
> OK.  How about adding the mouse-3 key binding without removing the mouse-2 
> one?

Fine with me, but that button is already bound to
mouse-save-then-kill.  I never use it, but what will those who do say?