Fix some hackificator odds and ends in wp-admin:

* `wp-activate.php` and `wp-admin/themes.php` don't need the closing PHP tag
* Switch single quotes for HTML attribute values to double in a few places
* Convert `include_once file.php` syntax to `include_once( 'file.php' )`
* Add access modifiers to methods/members in: `_WP_List_Table_Compat`, `Walker_Nav_Menu_Edit`, `Walker_Nav_Menu_Checklist`, `WP_Screen`, `Walker_Category_Checklist`
* `edit_user()` doesn't need to import the `$wpdb` global
* `wp_list_widgets()` doesn't need to import the `$sidebars_widgets` global
* switch/endswitch syntax is not supported in Hack
* A `<ul>` in `wp-admin/users.php` is unclosed

See #27881.


git-svn-id: https://develop.svn.wordpress.org/trunk@28500 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-activate.php

@@ -128,4 +128,4 @@ get_header();
 	var key_input = document.getElementById('key');
 	key_input && key_input.focus();
 </script>
-<?php get_footer(); ?>
+<?php get_footer();