grafx - Extensible Java Graphics Package Code

Adding a private constructor to FloatPolyClipper.

Renaming DepthPolyClipper to GouraudPolyClipper, DepthPolyEdge to
GouraudPolyEdge, and DepthPolyEdgePool to GouraudPolyEdgePool. I want to make
a parallel set of objects that do flat shading; I decided that having the same
edge class do both would be a bit confusing in the code.

Adding a comma in a comment.

Adding some cool options to Donut: CLIPPING_DEMO & COARSE_MESH.

Streamlining instantiations of DepthPolyEdge.

Adding class DepthPolyEdgePool. This is to recycle edges.

Paving the way for instance reuse of DepthPolyEdge.

Making some optimizations to Donut.

Making it possible to reuse a FloatColor instance.

Making some final improvements to Donut. The debugging code has been removed
for example.