bug#15868: 24.3.50; `display-buffer-other-frame' does not always use other frame

[martin rudalics]

> emacs -Q
>
> C-x 2
> C-x b *Messages*
> C-x 5 C-o *scratch*
>
> *scratch* is not displayed in another frame.
>
> Either the behavior should be what the doc currently says
> or the doc should specify what the behavior currently is.

Fixed in revision 115072 on trunk.

Thanks, martin