trash_ctor
trash_ctor(m->m_ext.ext_buf, MCLBYTES, zone_clust, how);
zone->uz_ctor != trash_ctor)
trash_ctor(item, size, zone, flags);
(void)trash_ctor(mem, size, NULL, 0);
int trash_ctor(void *mem, int size, void *arg, int flags);