menu_link_save() does not recursively check for equality between the $item and the $existing_item

If a menu_link entry only has changes within its ['options'], the db_update query may not be invoked.
The issue is in the following logic:

array_intersect_key($item, $existing_item) != $existing_item

The above code will only make a shallow comparison of the two arrays; array keys & values within the 'options' key can be different and the above logic will return FALSE, when TRUE is expected.