Updates:
* Hlwys provided a near-complete copy of the 531 cache: https://archive.openrs2.org/caches/667
* Hlwys provided copies of 508 and what is currently marked as 671 (though the revisions are unclear). These already existed but they have uncovered a few additional files.
* Hlwys provided a copy of 647. This also already existed but it uncovered 3 new files from other caches.