Rename split-window-{above-each-other|split-window-side-by-side}
to split-window-below and split-window-right.
* lisp/window.el (split-window-below, split-window-right): Rename from
split-window-above-each-other and split-window-side-by-side
respectively. All callers changed.
(split-window-sensibly, split-window-sensibly): Use them.
(split-window-keep-point): Doc fix.
* lisp/isearch.el: Add isearch-scroll property to split-window-below
and split-window-right.