grafx - Extensible Java Graphics Package Code

Adding VIEWPORT_CLIPPING to Donut 3D demo.

Simplifying drawPoint(), updating comments there, running the fringe cases
through the test again. Adding helpful comments in line-drawing routines.
Swapping the constant color polygon fill with the color-interpolated polygon
fill, putting the constant color up top. Simple code first. Followed the same
strategy with line-drawing code: have already put the single color line-draw
first. Final read-through. Looks good. I want to add some test scenarios
to Donut, then release new versions of grafx and grafx_3d.

Fixing the clear() incorrectness in 3D rendering library.

Making additional check that 'span > 0' for m_customPix.clearScanLine().

Adding comment for future direction.

Donut with optimized settings. Squeezing out frame rendering in less than 2
milliseconds, which is really good.

Now using poly() function in RasterDepthGraphics.

Removing the drawPoint() from line-drawing routines; if deltaX and deltaY are
both infinitesimally small, render nothing. In this same commit I'm adding
the GRENZE_EINS_UNTEN/GRENZE_EINS_OBEN technology. Unfortunately I am mixing
these into the same commit; I'm still sleepy.

Moving great big comment related to degenerate deltaX and deltaY. Defining
LINE_MINIMUM_DELTA_XY.

Changing the 2 locations of line-drawing code, doing a swap. Constant color
comes first. Unfortunately I mixed in a huge new comment in there.