grafx - Extensible Java Graphics Package Code

in 2D graphics, simplifying polygon fill a little bit by using 'odd' instead of
'even' in local variable name.

Removing one excessive 'if' branch, which checks that 'xStart < xEnd'. We go
ahead and do the expensive setup computations even if this isn't the case,
because that zero-length scanline for the part of the polygon is rather rare.

Oops, in polygon fill optimization changing nomenclature:
y0 -> z0
y1 -> z1
These were named incorrectly even though the code is the same.

Still simplifying the polygon fill, bit by bit.

Further optimizations in polygon filling, avoiding repeated array lookup.

Adding m_offset to RasterDepthGraphics but as I was incorporating it I realized
that there may be some performance gains to be had in fillPolygon(), the
simplest version of that method.

Still working on Javadoc in new constructor.

The new RasterDepthGraphics constructor now has five additional input
parameters.

Adding new constructor to RasterDepthGraphics. Not done yet. I think two more
"shift" parameters will be needed, and the implementation of course.

Fixing SteepLine with recent API changes.