Chess Game Fix

[MostlyKIGuess]

Fixes #1678 .

• here's the preview of me running the same game:

sugarlabs.mp4

Changes Made:

• Worked on correcting the conditions as per the README of https://github.com/douglasbagnall/p4wn/tree/master .
• The previous conditions was checking perhaps the possibility of the draw and not the draw actually. So it was not needed.
• Essentially it was implementing what was already implemented in the engine, check
  P4_MOVE_FLAG_DRAW = 64 a draw is available from the README.

Further Improvements

• The engine is kind of old, I have added comments to understand what conditions is doing what operations. And it just repeats move so once the kid learns to beat one level he can just repeat the moves to do the same.
• We can use the engine's p4_move2string function to easy our approach in the game. ( I shall perhaps create an issue on this and then work on this).
• Further tests from the original library can be added if using the same engine.

[MostlyKIGuess]

@llaske I have tested it for almost all the cases, 3 fold repetation works, win from both the players work, stalemate as well, to get stalemate checked what you can do is, keep the difficulty the lowest and play absolute horrible chess, the opponent will not try to mate you but staemate instead.

[llaske]

Nice. Thanks.