Fix for strict errors

Attempt to fix:
Strict warning: Declaration of com_webaccessglobal_Intuit::singleton() should be compatible with & CRM_Core_Payment::singleton($mode, &$paymentProcessor, &$paymentForm = NULL, $force = false) in require_once() (line 25 of [server_root]/public_html/sites/all/civi_extensions/intuit/Intuitpayment.php)