GNUmifluz: CIRCLEQ_INSERT_BEFORE

do { \
 (elm)->field.cqe_next = (listelm); \
 (elm)->field.cqe_prev = (listelm)->field.cqe_prev; \
 if ((listelm)->field.cqe_prev == (void *)(head)) \
 (head)->cqh_first = (elm); \
 else \
 (listelm)->field.cqe_prev->field.cqe_next = (elm); \
 (listelm)->field.cqe_prev = (elm); \
} while (0)