Pass $form_state to block configure forms

The proposed way to provide a block with a configuration form is hook_block_configure. The problem is that you cannot use AJAX in that form because you do not have $form_state at your disposal. The way to do AJAX-enable a block configuration form in D7 is hook_form_alter().
This simple patch simply passes $form_state to hook_block_configure(), so that you can provide AJAX-enabled forms right there in hook_block_configure(). You can, of course, still use hook_form_alter().