Fix for ScoreKBNK routine

[Chua Kong Sian]

The ScoreKBNK () routine in pl 67 does not quite work. The following
2 lines have to be added just before the return (s); statement like so.

s -= (8*taxicab(king1,king2) + 2*distance(Nsq,king2) +
distance(Bsq,king2));
s += KingEnding[king1];
return (s);

This seems to work fine now. I've tested a few KBNK positions and
with self play, gnu is able to mate itself in less than 35 moves most
of the time.

Regards.

Kong Sian