Splines are not dashed.

The polygon tessellation routine has problems. It appears that the
following paper has the right answers:

	http://cm.bell-labs.com/cm/cs/doc/93/2-27.ps.gz

	[Hobby93c] John D. Hobby, Practical Segment Intersection with
	Finite Precision Output, Computation Geometry Theory and
	Applications, 13(4), 1999.

Stroking a self-intersecting path generates the wrong answer, (in
mostly subtle ways). The fix is to tessellate a giant polygon for the
entire stroke outline rather than incrementally generating trapezoids.