Optimize isSubclassOf checks
Optimize isSubclassOf checks

- Suggested by @marc-mabe -- if is_subclass_of() returns true, we can return
  immediately. This allows us to skip the version_compare() when it passes.
- Removed Zend\Stdlib\SubClass, as I evidently missed doing so in zendframework/zf2#1852

MadCat34/zend-xmlrpc,zendframework/zend-xmlrpc,samsonasik/zend-xmlrpc