Changed ad_register_filter so that it registers the filter immediately in case it is called after server-initialization is completed. This makes it suitable as a drop-in replacement for ns_register_filter.
moved the 5.1.1-5.1.2 upgrade script back to 5.1.1d2-5.1.1d3 and changed info file from 5.1.2 to 5.1.1d3, to maintain consistency with core release conventions.