Fix imported top level menus lacking the menu-top class. This is because submenus no longer have the menu-top class by default, so submenu items moved to the top level would also be missing it.

git-svn-id: https://plugins.svn.wordpress.org/admin-menu-editor/trunk@952889 b8457f37-d9ea-0310-8a92-e5e31aec5664