Refactoring: removed all traces of old MonoSplitter algorithm and
shortened new algorithm
removed: doSplit, alyTrap, vectorLength, dotProd, crossProd, mapAngle,
find_first_inside, createMonoSegment, newMonoChain,
get_out_segment_next_right_of, splitPolygonChain,
normalize_monotone_chains, alyTrap_check, mock*, test_TL_BL...,
test_monotonate_trapezoids2, test_mapAngle, check_monoChains_noDoublePts,
checkMonoChainVertexIDs, check_vertexChain_monoChainDoubleLinks,
test_vertices_monoChain, test_splitPolygonChain*, test_equal_next_right_of
new: nbVertices, appendDiagonalsEntry, nbMonoSubPolys,
copyMonoChainsFromSegments, get_visibilityMap
create_mono_chains: MonoSplitter -> PolygonData
unique_monotone_chains_max: extracts monochains from all segments not just
from designated start segments