Fix disambiguation page that were never properly migrated from 1.4
mysql> explain SELECT 'Disambiguations' as type,la.pl_namespace AS namespace,
la.pl_title AS title, la.pl_from AS link_from
FROM `pagelinks` AS la, `pagelinks` AS lb, `page` AS pa, `page` AS pb
WHERE pb.page_namespace = 4
AND pb.page_title = 'Liens_aux_pages_d\'homonymie'
AND lb.pl_title = pb.page_title
AND pa.page_id = lb.pl_from
AND la.pl_title = pa.page_title;
---+------+----------+----------+-----+-----------+----+--------------+
tab|type |possible k|key |k_len|ref |rows|Extra |
---+------+----------+----------+-----+-----------+----+--------------+
pb |const |name_title|name_title| 259|const,const| 1|index |
la |index |NULL |pl_from | 263|NULL |1976|index |
lb |index |pl_from |pl_from | 263|NULL |1976|where & index |
pa |eq_ref|PRIMARY |PRIMARY | 4|lb.pl_from | 1|where |
---+------+----------+----------+-----+-----------+----+--------------+