Add two test cases, point-on-segment and point-on-vertex.

Curious detail of the tests is that points of interest have nearly exact X of tested points, the values differ after 14th decimal place.
The tests provided test geometries for intersection with and without coordinates trimming after the 14th place (as per Martin Davis suggestion).
It has been extensively discussed in Ticket #591 and https://github.com/libgeos/libgeos/pull/40 with Martin Davis' input.


git-svn-id: http://svn.osgeo.org/geos/trunk@4038 5242fede-7e19-0410-aef8-94bd7d2200fb