update OpenGIS for XLink change
Brought to you by:
pabigot
Per http://www.ogcnetwork.net/node/1829, as of 21Jul2012 all OpenGIS schema shall use the official W3C xlink instead of the OGC variant. PyXB's support will transition to this version as of the 1.20.0 release.
Fixed in the 1.2.x series. The fix will not be back-ported to the 1.1.x series.