Scrolling commands which does not signal errors at top/bottom.

Scrolling commands which does not signal errors at top/bottom.
http://lists.gnu.org/archive/html/emacs-devel/2010-03/msg01452.html

* simple.el (scroll-up-command, scroll-down-command): New commands.
Put property isearch-scroll=t on them.

* bindings.el (global-map): Rebind [prior] from `scroll-down' to
`scroll-down-command' and [next] from `scroll-up' to
`scroll-up-command'.

* emulation/cua-base.el: Put property CUA=move on
`scroll-up-command' and `scroll-down-command'.
(cua--init-keymaps): Remap `scroll-up-command' to `cua-scroll-up'
and `scroll-down-command' to `cua-scroll-down'.