bug#68081: 30.0.50; derived-mode and display-buffer-alist

[martin rudalics]

Attached find a patch for info.el on master that should handle all cases
I found in a fairly sane way.  Please test it with the info commands you
know of.

I've not eliminated things like

  (save-window-excursion
    (or (derived-mode-p 'Info-mode) (info-pop-to-buffer))
    (Info-goto-node (Info-extract-pointer "next"))))

While these will hardly DTRT with multiple frames and occasionally
produce some flickering here, they allow to navigate info buffers that
are not displayed (however useful that is).

As for compilation modes, please provide an example of how they
misbehave.

Thanks, martin

info.el.diff
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