Added support for parent::__construct() in Aoe_JsCssTstamp_Model_Package...

... now that it exists in Magento CE 1.9.0.1 and EE 1.14.0.1.

In the newest versions of Magento, Mage_Core_Model_Design_Package has a __construct() method, so we need to call it in order for the rewrite to correctly execute the functionality in the parent.