bug#1305: All code that currently beeps should use visual bell instead

[Eli Zaretskii]

> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Thu, 29 Apr 2021 23:17:58 +0300
> Cc: Alan Third <alan@idiocy.org>, 1305@debbugs.gnu.org,
>  Michael Welsh Duggan <mwd@md5i.com>, Stefan Kangas <stefan@marxist.se>,
>  jasonspiro4@gmail.com, Stefan Monnier <monnier@iro.umontreal.ca>,
>  Lars Ingebrigtsen <larsi@gnus.org>
> 
> > I can't really say whether it's better or worse, with visible-bell t on 
> > Windows the frame briefly flashes (with the FlashWindow function), a bit 
> > like a flash in a terminal.  Among the three visible-bell t behaviors, 
> > it's the best one IMO, in the sense that it's visible and not intrusive.
> 
> Is it possible to replicate on other systems?

Just so we are on the same page: FlashWindow on MS-Windows doesn't
necessarily flash the frame.  Or maybe I don't understand what Gregory
meant by that.