grafx - Extensible Java Graphics Package Code

The ComputerPlayer is now honoring all possible post drop movements, and these
have been somewhat tested. Right now it seems as if the AI only chooses slide
moves in the positive x direction, for some reason.

Renaming m_postDropSlide to m_postDropAction.

Default level for computer player changes from 23 to 21. This is the 4x4 pit
consisting of just 5-er blocks except for the long piece.

There are 1224 distinct blocks and 1223 distinct hashCode() values. In other
words there is a single collision.

Moving from java.util.Hashtable to java.util.HashMap.

Implemented Block.hashCode().

Starting to add hashCode() to Layer and to Block.

Adding hashCode() to Position and to HalfPosition.

Adding equals() methods.

Getting the computer player to run again after the massive changes to
BlockOrientation structure (in BlockGenerator) and with the introduction of the
16 bit "short" bit fields which specify the post-drop action.