[Tile-serving] [osm2pgsql] Change z_order of link roads and add tests (#374)

[Paul Norman]

Since the HOT style still has z_ordering issues, I installed it was able to verify the changes work

![image](https://cloud.githubusercontent.com/assets/1190866/8587509/d188ac7c-25b1-11e5-8cdf-e55c76c5a6dd.png)
![image](https://cloud.githubusercontent.com/assets/1190866/8587515/e1393394-25b1-11e5-912b-7669652e969a.png)

---
Reply to this email directly or view it on GitHub:
https://github.com/openstreetmap/osm2pgsql/pull/374#issuecomment-119805184
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/tile-serving/attachments/20150708/a53243c0/attachment.html>