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

[Gregory Heytings]

> > Or do we need a complete rethinking of this?  Perhaps there is some 
> > other software that we can steal some good ideas from?  (And if we can 
> > come up with something very good, perhaps we will want to do the same 
> > on GNU/Linux.)
>
> That's a good idea.  What does (for instance) Libreoffice or Excel do to 
> signal a user error or "end of search" and stuff like that?

LibreOffice does very little: when the string is not found at all in the 
document it turns red and a "Search key not found" message is displayed at 
the end of the search bar; when you reach the last occurrence a "Reached 
the end of the document" is displayed in the search bar and the search 
wraps silently.  For other errors, LibreOffice does even less, for example 
if you paste and there is nothing to paste, nothing happens, and that's 
all.

For Microsoft Office, I don't know, but from what I remember the error 
handling was similar.