This changes the original tests so that it splits the original path
into two sub paths. When adding a new block to the copied path it also
adds another sub path. This further stresses the path copying
mechanism and exposes a bug.
It also tests intersections by drawing a self-intersecting path and a
path with two sub-paths that overlap. Where the path overlaps it
should be inverted.
This tests various paths drawing rectangles and verifies that the
expected pixels are filled in. Some of the paths are drawn by copying
an existing path and modifying it which should test the copy-on-write
code.
