0029511: Section fails for these two faces

0029511: Section fails for these two faces

Modified method: Approx_ComputeLine::Compute
Check of multicurve is now always unconditional, the procedure of check is modified to avoid infinite loops.

Modified classes: GeomLib_CheckBSplineCurve and GeomLib_Check2dBSplineCurve
Correction of poles at the ends of curve is modified to fit the direction of tangent defined by two first points or two last points of walking line.

Also modified:

BOPAlgo_PaveFiller: modified methods PostTreatFF, RemoveUsedVertices - now unused vertices are included in the list of vertices to be absorbed by other ones.