cq_prev_l
(list)->cq_prev_l = (list); \
(list)->cq_prev_l->cq_next_l = (elem); \
(list)->cq_prev_l = (elem); \
(fst)->cq_prev_l->cq_next_l = (snd)->cq_next_l; \
(snd)->cq_next_l->cq_prev_l = (fst)->cq_prev_l; \
(snd)->cq_prev_l->cq_next_l = (fst); \
(fst)->cq_prev_l = (snd)->cq_prev_l; \
(elem)->cq_prev_l->cq_next_e = (elem)->cq_next_e; \