validate hook does not return errors array properly in J16+

in Joomla 1.6+, the validate hook does not work correctly. while the hook itself is recognized, the errors array that should be returned is ignored by the form and so no validation occurs. the error would impact any hooks that work by returning a value to the parent code rather than handling with variables passed by reference (the more common behavior).

see also: http://forum.civicrm.org/index.php/topic,22781.0.html