Move is_subclass_of code to Zend\Stdlib
Move is_subclass_of code to Zend\Stdlib

@see https://bugs.php.net/bug.php?id=53727

This code is used to determine the subclass of a given class. Used in Zend\Di, Zend\Form,
Zend\InfoCard, Zend\Loader, Zend\Mvc, Zend\ServiceManager and Zend\XmlRpc

ezimuel/zend-mvc,svycka/zend-mvc,MadCat34/zend-mvc,svycka/zend-mvc,ezimuel/zend-mvc,turrsis/zend-mvc,MadCat34/zend-mvc,turrsis/zend-mvc