(defun goto-next-window (&optional arg)
  (interactive "P")
  (cond ((one-window-p)
         (select-window (split-window-horizontally)))
        (arg (other-window -1))
        (t (other-window 1))))
(global-set-key "\C-o" 'goto-next-window)
(global-set-key "\M-\C-o" 'open-line)