SnapRoundingNoder fix

[mngr777]

Fix for "GEOSGeom_setPrecision returns error for valid geometry" https://trac.osgeo.org/geos/ticket/1127

nearnessTol calculation moved from SnapRoundingIntersectionAdder to SnapRoundingNoder; same tolerance value is passed to MCIndexNoder. This allows to detect all cases of vertices positioned close enough to segments to be added as intersections by SnapRoundingIntersectionAdder::processNearVertex. Currently closely positioned segments can be filtered out in MonotoneChain::computeOverlaps() by MonotoneChain::overlaps() called with zero overlapTolerance.

[Komzpa]

@mngr777 can you please add the minimized test case to the suite so it won't break in the future?
Thanks.

[pramsey]

@dr-jts is going to check this fix on JTS too, just to make sure. Seems pretty magical.

[dr-jts]

NIce work on finding this bug. I fixed it in SnappingNoder, but of course SnapRoundingNoder needs the same thing. Glad the fix is so simple (and not some fundamental design flaw in the Snap-Rounding approach!).

[dr-jts]

Unfortunately it looks to me like this fix (although correct) does not solve 2 of the 3 test cases for in the original GEOS issue. @mngr777 can you confirm if you are still seeing this issue in GeometryPrecisionReducer? If so, we should reopen an issue for this, and capture the failing test cases.

(Note: the fix I suggested of reducing the precision of the scale factor still works, although it is awkward to do using the current C API).

[mngr777]

@dr-jts Yes, 2 cases still produce exceptions. Please reopen the issue.