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

[Gregory Heytings]

> > I checked on macOS, and the only apps (at least, the only apps among 
> > the ones I use) that repeatedly beep are the terminal and Emacs. Other 
> > apps only beep when you do something "wrong", that is, when they cannot 
> > do what you want (for example when you ask the program to paste 
> > something when there is nothing to paste), or when they open an 
> > important dialog.  The terminal also beeps when it cannot do what you 
> > want (for example when you press TAB and it cannot complete the current 
> > input).  In comparison, Emacs beeps a lot.
>
> Really?  I find that, in general, Emacs only beeps when it cannot do 
> what I want (for example, C-n at EOB) or I cancel an operation (C-g or 
> ESC ESC ESC).  Under what other circumstances are you encountering 
> beeping?

For example, every time you press C-g, and every time you search for 
something that it cannot find.  When you press C-g Emacs does what you 
want, so why beep?  When you search for something that isn't there you 
already see that it isn't there, so why beep?