square_opp         98 src/pst.cpp    static int square_opp  (int square);
square_opp        214 src/pst.cpp          P(piece,square_opp(sq),Opening) += BishopDiagonalOpening;
square_opp        302 src/pst.cpp                P(piece+1,sq,stage) = -P(piece,square_opp(sq),stage); // HACK