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

[Drew Adams]

> >> My point was that we can clean up without any new variable ;-)
> > I'm not sure I follow you at all here.  :-/
> 
> Stefan M means (IIUC) that, instead of introducing a new variable to
> clean up the current situation, it is better to reuse the already existing
> ring-bell-function variable, to give it some new possible values,

+1.

> and at the same time to deprecate the visible-bell variable.

Is that needed?