(nxtitemp, trade_getitem, trade_desc, trade_check_item_ok, nxtitem,

oprange, show_mission, nameofitem, build_mission_list_type,
unit_map, xdvisible, trdswitchown, ontradingblock, trad, check_trade,
unit_type_name, start_stop_unit, scut, scra, mission, multifire,
perform_mission, fuel, NSC_GENITEM): Replace struct genitem with
struct empobj.  Remove genitem.h and create a new file empobj.h.
Replace multiple instances of unions of ef_type structures with
one standard union empobj_storage which is a superset of the individual
instances.

src/lib/commands/xdump.c

@@ -197,7 +197,7 @@ xdftr(int n)
 static int
 xdvisible(int type, void *p)
 {
-    struct genitem *gp = p;
+    struct empobj *gp = p;
     struct trtstr *tp = p;
     struct lonstr *lp = p;
     struct natstr *natp;