(string) requireZendLoader ()
Detect and return the path to current Zend loader class.
Starting from ZF 0.9.0 autoloading function has been moved from Zend.php to Zend/Loader.php class. Starting from ZF 1.0.0 Zend.php class no longer exists.
This function tries to detect whether Zend_Loader exists and returns its path if yes. If the first step fails, the class will try to find Zend.php library available in ZF <= 0.9.0 and returns its path if its exists.
If neither Zend/Loader.php nor Zend.php exists, then this function will raise a sfAutoloadException exception.
returns Path to default Zend Loader class
throws sfAutoloadException
