grafx - Extensible Java Graphics Package 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.

Adding beginnings of class RasterDepthPixBuff.

Fixing Javadoc generation script.

Adding package desriptions, in the form of 'package.html' files, to packages
that should appear in release Javadoc.

Taking away the 'public' access modifier from ImageConsumerChain, making it
package visible. This is to unclutter the Javadoc, since nobody uses it.