Make ST_ChangeEdgeGeom motion collision detection code more robust

The new model avoids a call to GEOSSymDifference but rather checks
each candidate node against both "motion ranges" containment.
It still constructs something, but only MULTIPOINT, which should
be safe. Haven't profiled but the new code should also be faster
than the previous. Fixes ticket #2176, includes testcase for it.

git-svn-id: http://svn.osgeo.org/postgis/branches/2.0@10983 b70326c6-7e19-0410-871a-916f4a2858ee