(ITEM_MAX): New, value 9999.

(give, deliver_it): Use it instead of 9990.
(load_comm_ship, load_comm_land, rese): Use it instead of 9999.
(thre): Use it instead of 10000.
(check_market, explore, move, pln_dropoff): Use it instead of 32767.
(unload_it): Use it instead of 99999 (which couldn't possibly work,
but what do you expect from the autonav code).

src/lib/subs/plnsub.c

@@ -240,7 +240,7 @@ pln_dropoff(struct emp_qelem *list, struct ichrstr *ip, coord tx, coord ty,
 	    return;
 	}
 	there = sectp->sct_item[ip->i_vtype];
-	max = 32767;
+	max = ITEM_MAX;
     } else {
 	sp = ptr;
 	there = sp->shp_item[ip->i_vtype];