Different behavior for vgpdf paths

Original [issue 128](https://code.google.com/p/plotinum/issues/detail?id=128) created by eaburns on 2013-06-08T12:44:54.000Z:

All other vg backends seem to insert an implicit Move to the start of a new path, and they seem to insert Lines between disjoint path components.

For example, if you draw two arcs with the same center point but different radii then call p.Close, vgpdf doesn't draw anything (because the path has a discontinuity) but all other backends draw a sector.