message_queue_purge
size_t message_queue_purge(struct filed *f, size_t, int);
sum += message_queue_purge(f,
sum += message_queue_purge(f, 0, PURGE_BY_PRIORITY);
message_queue_purge(f, 0, PURGE_BY_PRIORITY);
&& message_queue_purge(f, 1, PURGE_OLDEST))