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

[Gregory Heytings]

> > Yes, "flash" is perhaps not the best word here, perhaps "vibrate" is 
> > better.
>
> That word still doesn't tell me what you think happens.  Can you 
> describe in more detail what exactly you see, and on which version of 
> MS-Windows?

Windows 10.

I don't know how to describe this better than with the words "flash" or 
"vibrate", so I looked at the docs:

"Flashing a window means changing the appearance of its caption bar as if 
the window were changing from inactive to active status, or vice versa. 
[...] Typically, a window is flashed to inform the user that the window 
requires attention but that it does not currently have the keyboard 
focus." [1]

[1] 
https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-flashwindow

But even that doesn't describe the effect accurately, the feeling I have 
is closer to "the frame briefly vibrates".  As I said, I use Windows only 
rarely, so my feeling is perhaps not right.