bug#51210: Customizable other-window-for-scrolling

[martin rudalics]

>> Maybe a variable 'other-window-scroll-window' whose value could be a
>> function to get that window.
>
> Since there is already the word "window" in the function name,
> maybe better would be 'other-window-scroll-default' that hints
> that it overrides the default that is the next window:

Since we already have 'other-window-scroll-buffer' this might be
confusing.  And shouldn't a window, if specified, override a specified
buffer?  BTW I think we should move 'other-window-for-scrolling' to
window.el - all it does is call Lisp primitives.  And turn
scroll_command into 'Fscroll_command' (or, better 'Fscroll_window') so
things like 'scroll-down' (or, better 'scroll-window-down') and
'scroll-other-window-down' could end up in window.el too.  But maybe I'm
missing some important detail.

martin