Improve the custom scoll functions

This way they won't go to the next page if they can scroll enough,
only when the en of a page has been reached will they go to the next
one.

emacs/init.el

@@ -593,22 +593,28 @@ Also change directories to current working directory."
   "Either scroll down or go to the previous page.
 
 Depending on the value of `buffer-narrowed-p'."
-  (interactive "P")
+  (interactive "^P")
   (if (buffer-narrowed-p)
-      (progn
-        (narrow-to-page (or arg -1))
-        (goto-char (point-min)))
+      (let ((scroll-error-top-bottom nil))
+        (condition-case nil
+            (scroll-down-command arg)
+          (beginning-of-buffer
+           (narrow-to-page -1)
+           (goto-char (point-min)))))
     (scroll-down-command arg)))
 
 (defun oni:scroll-up-or-next-page (arg)
   "Either scroll up or go to the next page.
 
 Depending on the value of `buffer-narrowed-p'."
-  (interactive "P")
+  (interactive "^P")
   (if (buffer-narrowed-p)
-      (progn
-        (narrow-to-page (or arg 1))
-        (goto-char (point-min)))
+      (let ((scroll-error-top-bottom nil))
+        (condition-case nil
+            (scroll-up-command arg)
+          (end-of-buffer
+           (narrow-to-page 1)
+           (goto-char (point-min)))))
     (scroll-up-command arg)))
 
 (global-set-key (kbd "<prior>") 'oni:scroll-down-or-prev-page)