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-admin/media.php

@@ -14,7 +14,7 @@ $submenu_file = 'upload.php';
 
 wp_reset_vars(array('action'));
 
-switch( $action ) :
+switch ( $action ) {
 case 'editattachment' :
 	$attachment_id = (int) $_POST['attachment_id'];
 	check_admin_referer('media-form');
@@ -143,4 +143,4 @@ default:
 	wp_redirect( admin_url('upload.php') );
 	exit;
 
-endswitch;
+}