Track which items have been listed on the AH using a new protected table
and trigger. Only show these items in the AH by default. This is controlled
by the `search.OMIT_NO_HISTORY` setting and is now on by default.
Run the following query to populate the new table using your existing
auction house history:
```
INSERT IGNORE INTO auction_house_items(itemid)
SELECT itemid FROM auction_house
GROUP BY itemid;
```
