bug#25115: 26.0.50; ibuffer fails to show confirmation buffer when there are side windows

[martin rudalics]

> I don't use ibuffer often, but I have been changing instances of
> switch-to-buffer to pop-to-buffer-same-window since reading Bug#22244.
>
> Makes me wonder about switch-to-buffer's future

This is not primarily about ‘switch-to-buffer’.  It's about displaying a
list of items (file or buffer names, completions, ispell's choices, ...)
in a buffer, temporarily showing that buffer in a window and then
proceeding in reaction to user input.  ‘dired-mark-pop-up’ is a typical
function for this purpose.

ibuffer apparently uses the last window in ‘window-list’ to show the
buffer at the bottom of the frame, something ‘display-buffer-at-bottom’
should handle well.  But I'd like to hear the opinion of a long time
user of ‘ibuffer’ before actually changing this.

Also, ‘ibuffer-confirm-operation-on’ does ‘fit-window-to-buffer’ and I'd
prefer fixing bug#25055 first before reintroducing it somewhere else ;-)

martin