API: (bug 16549) Kill a filesort in list=allpages&apfilterlanglinks=withlanglinks...

API: (bug 16549) Kill a filesort in list=allpages&apfilterlanglinks=withlanglinks by replacing DISTINCT with GROUP BY. Of course GROUP BY page_namespace, page_title would suffice on MySQL, but Postgres will reportedly whine about that being against the SQL standard. Using GROUP BY on all selected fields instead (should please pgsql) and taking care that page_namespace, page_title is on front, which shouldn't cause a filesort is MySQL is smart enough (5.0 is, let's just hope 4.1 is too)