D5->D6: New parameter for form builder functions

If the form-id passed to drupal_get_form() is found as a function name, then that function is called to build the form, and any additional arguments to drupal_get_form() are passed on to the form constructor function.

Starting with D6, these form builder functions receive the new &$form_state as arg0.

See the second part of http://drupal.org/node/144132#multistep.

It would be helpful to have this check added to the upgrading checks.

Thanks for a very useful module!