Move most instances of new WP_User to get_userdata(). see #21120.

git-svn-id: http://core.svn.wordpress.org/trunk@21413 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/user.php

@@ -198,7 +198,7 @@ function get_editable_roles() {
  * @return object WP_User object with user data.
  */
 function get_user_to_edit( $user_id ) {
-	$user = new WP_User( $user_id );
+	$user = get_userdata( $user_id );
 
 	$user->filter = 'edit';