deltamap_remove
me = deltamap_remove(ul->un_deltamap, mof, nb);
menext = deltamap_remove(mtm, mof, nb);
me = deltamap_remove(ul->un_deltamap,
me = deltamap_remove(ul->un_deltamap, vamof, nb);
extern mapentry_t *deltamap_remove(mt_map_t *, offset_t, off_t);