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

[Gregory Heytings]

> > > 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.

Yes, "flash" is perhaps not the best word here, perhaps "vibrate" is 
better.

And no, I don't think it is possible to replicate that behavior on other 
systems, it's a "window manager" primitive, which AFAIU exists on Windows 
but not on macOS or GNU/Linux.