bug#26513: 25.2; pop-up-frames and *Completions* buffer

[martin rudalics]

> I have a `display-buffer-alist` entry that does all kinds of funny
> things for *Completions* ;-)

Please post it here.

> No objection to the patch, but the amount of code duplication in it
> (both in the new lines and in the surrounding code) suggests we may want
> to refactor some of that code so that the options processing code is
> written at a single place "once" rather than
> once-per-display-buffer-function.

Agreed.  But I profoundly dislike the sole idea of abusing
'redirect-frame-focus' for fixing this kind of problems.

martin