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

[Eli Zaretskii]

> Date: Sun, 18 Apr 2021 18:23:57 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 1305@debbugs.gnu.org, mwd@md5i.com, stefan@marxist.se, 
> gregory@heytings.org,
>  jasonspiro4@gmail.com, monnier@iro.umontreal.ca
> 
> If you put a breakpoint inside tty_ring_bell, do you see that
> tty->TS_visible_bell is non-NULL or not?  If it's non-NULL, perhaps
> the terminal emulator has that disabled somehow?

For example, PuTTY lets you customize what the bell does, so perhaps
xterm and other emulators do as well?