Set no longer extend Object in CakePHP 1.3.0

[joelpet]

As it says on http://book.cakephp.org/view/1561/Migrating-from-CakePHP-1-2-to-1-3 Set does no longer extend Object in CakePHP 1.3.0. That means the following source code lines will generate an error:

286: && Set::isEqual($this->newGroups, $this->oldGroups)) {
291: if ($this->newGroups && !Set::isEqual($this->newGroups, $this->oldGroups)) {