bug#60886: 29.0.60; split-root-window-below broken for split-window-keep-point

[Juri Linkov]

>> I proposed the same in bug#56767.
>
> That would have avoided nonsense like retrieving 'window-point' of an
> uninvolved window or the 'quit-restore' parameter of an internal window.

Then I don't know what to do at this time before the release:
whether to rewrite them or not.

Also these commands are missing:

(defun split-root-window-above (&optional size)
  (interactive "P")
  (when (and size (< size 0) (< (- size) window-min-height))
    ;; `split-window' would not signal an error here.
    (error "Size of new window too small"))
  (split-window (frame-root-window) size 'above))

(defun split-root-window-left (&optional size)
  (interactive "P")
  (when (and size (< size 0) (< (- size) window-min-width))
    ;; `split-window' would not signal an error here.
    (error "Size of new window too small"))
  (split-window (frame-root-window) size 'left))

There are no corresponding split-window-above and split-window-left,
because they provide the same result as the existing
split-window-below and split-window-right.  But there is no way
to add a window on the left/above for the root window
by using split-root-window-below or split-root-window-right.
Therefore split-root-window-above and split-root-window-left
are needed.