Make it possible to change menu position using the "custom_admin_menu" and "custom_admin_submenu" filters.

Previously menus were sorted *before* calling these filters, so position changes made by filter callbacks would be ignored.

git-svn-id: https://plugins.svn.wordpress.org/admin-menu-editor/trunk@997117 b8457f37-d9ea-0310-8a92-e5e31aec5664