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

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: stefan@marxist.se,  mwd@md5i.com,  gregory@heytings.org,
>   1305@debbugs.gnu.org,  jasonspiro4@gmail.com,  monnier@iro.umontreal.ca
> Date: Mon, 19 Apr 2021 14:56:38 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > 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?
> 
> Let's see...
> 
> gdb) print tty->TS_visible_bell 
> $1 = 0x555555da95c3 "\033[?5h$<100/>\033[?5l"

Then this should produce the same effect as "tput flash", I think.