destroying your own king is illegal */
#define F_FRC_TYPE_CASTLING 256 /* generate castlings as captures of own Rook */
#define F_MANDATORY_CAPTURE 0x200
+#define F_NULL_MOVE 0x400
/* Special epfile values. [HGM] positive values are non-reversible moves! */
#define EP_NONE (-6) /* [HGM] Tricky! order matters: */