bug#7728: 24.0.50; GDB backtrace from abort

[Drew Adams]

> >> Hmm... let's see... how 'bout `with-selected-frame'?  ;-)
> >
> > Does not exist before Emacs 23, for one thing.  My code 
> > needs to work with multiple Emacs versions.
> 
> If you can live with Emacs=22, then you can try (with-selected-window
> (frame-selected-window <frame>) ...).

That too is good to know.
But most of my code works for Emacs 20+.