[point_on_surface] Do multiply & divide as separate steps to preserve as much precision as possible when using integer coordinates.
[test][point_on_surface] Add test for point_on_surface using integer coordinates.
Merge pull request #157 from zerebubuth/integral_point_on_surface

Fix `point_on_surface` for integral coordinates
Merge remote-tracking branch 'origin/master' into ccw_point_on_surface

Conflicts:
	test/algorithms/point_on_surface.cpp
[extreme_points] s/kludge/factor/ when flipping side tests.