Submit the form when setting items per page option so it's visible straight away

git-svn-id: http://svn.automattic.com/wordpress/trunk@10987 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/admin.php

@@ -41,6 +41,8 @@ nocache_headers();
 
 update_category_cache();
 
+save_screen_options();
+
 $posts_per_page = get_option('posts_per_page');
 $what_to_show = get_option('what_to_show');
 $date_format = get_option('date_format');