I have just found an incredible bug in the zrf. Black cannot castle! It is
entirely my fault, I have playtested the game extensively against
Zillions, but always as White after I managed to introduce the Elephants.
(It is a symmetry thing, the move of the Elephant requires (symmetry e w)
and the like because of the usual (symmetry n s), and I didn't think to
replace e and w in the castling macros by (if (am-white) e else w) and
vice-versa.) Sorry about that!