These functions import $wpdb but do not use it.

See #27882.


git-svn-id: https://develop.svn.wordpress.org/trunk@28539 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/capabilities.php

@@ -140,7 +140,7 @@ class WP_Roles {
 		if ( ! $this->use_db )
 			return;
 
-		global $wpdb, $wp_user_roles;
+		global $wpdb;
 
 		// Duplicated from _init() to avoid an extra function call.
 		$this->role_key = $wpdb->get_blog_prefix() . 'user_roles';