#2 Intersection is not found when on a line end

[Jaime Soffer]

The current intersection code fails if the intersection
between two lines or line strips is exactly on the end
of one of those.

Technically that's perfectly right; such an snap is not
an intersection, but a tangential contact. However, the
design requires to specify a 'curve' as a line strip;
then, the intersection between two curves fails without
any kind of warning if it happens right at a vertex. It
is statistically frequent, more so if the curve has a
high degree of precision.

Suggested solution is to make a difference between
standard line strips and curves. To test for END on a
curve should return only the first and last vertex, and
to test for INT an special procedure should be implemented.