classq_tail
#define qtail(q) classq_tail(&(q)->que_) /* Tail of the queue */
if ((m0 = classq_tail(q)) != NULL)
classq_tail(q) = m;
if ((m = classq_tail(q)) == NULL)
classq_tail(q) = NULL;
if (classq_tail(from) == NULL)
if (classq_tail(to) == NULL) {
tail = classq_tail(from);
tail = classq_tail(to);
tail = classq_tail(from);
classq_tail(to) = tail;
classq_tail(from) = NULL;