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

git-svn-id: https://develop.svn.wordpress.org/trunk@10987 602fd350-edb4-49c9-b593-d223f7449a82

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');