clrbits
int setbits, clrbits, Xbits, op;
for (setbits = clrbits = Xbits = 0;; nset++) {
clrbits |= nset->bits;
clrbits &= ~nset->bits;
if (clrbits) {
set->bits = clrbits;
clrbits(clp->c_cq, clp->c_cf - clp->c_cs, cc);
clrbits(clp->c_cq, clp->c_cl - clp->c_cs, cc);
void clrbits(u_char *, int, int);