bug#20020: 25.0.50; `info-display-manual' should reuse existing window where buffer is displayed

[martin rudalics]

> Or perhaps `pop-to-buffer-same-window', since the command uses
> `switch-to-window' presently?

If I'm not mistaken, this would prefer the selected window to a window
on another frame.  So probably use 'display-buffer-reuse-window' as
first choice and 'display-buffer-same-window' as second choice.  With
a suitable 'reusable-frames' and an 'inhibit-same-window' nil alist
entries.

martin