How about making `set-minibuffer-window' obsolete?

[Alan Mackenzie]

Hello, Emacs.

Does anybody have any objection to me making set-minibuffer-window
obsolete?

It's defined in src/minibuf.c, but not used by any C function, and it's
not used by any Lisp in Emacs itself - the nearest to a use is a
commented out occurrence in lisp/textmodes/ispell.el.

This function just sets the C variable minibuf_window.  This variable is
defined (by comment) to be the minibuffer window of the selected frame.
So setting it to a random mini-window will cause nasty problems.

Actually, I'd prefer just to remove the function entirely - but there's
always the chance it's being used by some external library.

So, any objections?

-- 
Alan Mackenzie (Nuremberg, Germany).