grafx - Extensible Java Graphics Package Code

Adding new test code which exposes a bug: OnePixelSteepLine.

Backing out the last two commits in RasterDepthGraphics. I was modifying the
wrong section of code, and I just realized that first we should correct an
anomaly where a very short line segment which spans a very large z distance,
which has both endpoints aliased to the same pixel, should be handled more
correctly; the pixel in front should be given priority.

Unrolling the first iteration of 'while' loop in line drawing improvement
experimental code block.

Adding comments which announce that I will be focusing on a particular section
of code.

Adding test code: SteepLine. This is to better test optimizations made to the
use of bounded() on the z values when drawing lines.

Adding ZBITS_8 option.

In RasterDepthGraphics, allowing the choice between 16 bit and 24 bit z
buffering.

Incorporating the usage of RasterDepthPixBuff with almost no impact on
performance. Unfortunately this causes lots of duplicated code.

Starting to add support for RasterDepthPixBuff.

Fleshing out class/interface RasterDepthPixBuff.