Fix bare King adjudication

Fix bare King adjudication

The increase of the number of piece types to 66 gave the BlackKing code
131, wich is > 127, so that using a signed char for it makes it < 0.
This cause the black King in the adjudication code to be seen as a white
piece. When black then checkmates with 2 pieces, only 1 piece is seen
(Q), and then assumed to be a bare King! Now the piece value is passed
through an (int) to prevent this.