Speedup areal TopoJSON output routine to use edge walking

Now it takes 6% of the time to do the same thing !

Tweak tests to expect new arcs numbering and order.
Also fixes missing comma separating polygon ring arcs.

git-svn-id: http://svn.osgeo.org/postgis/trunk@11187 b70326c6-7e19-0410-871a-916f4a2858ee