Allow unbind onchange handler

In Drupal almost everything is alterable. And this is good :) But, in current module implementation, it's not possible to unbind onchange handler, which may be required for some customization. For example, in my case, I do custom ajaxification of a search page.

Of course, unbinding can be done with $(...).unbind('change'), but this will affect every handlers.

Attached patch changes nothing, but allows to unbind onchange handler with
$(...).unbind('change', Drupal.behaviors.facetapiSelect.goToLocation).

BTW, thanks for the module!