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.

Built from https://develop.svn.wordpress.org/trunk@28500


git-svn-id: http://core.svn.wordpress.org/trunk@28326 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/users.php

@@ -334,6 +334,7 @@ case 'remove':
 		}
  	}
  	?>
+</ul>
 <?php if ( $go_remove ) : ?>
 		<input type="hidden" name="action" value="doremove" />
 		<?php submit_button( __('Confirm Removal'), 'secondary' ); ?>