Duel allocation (#2734)

* Duels are now dynamically created and no longer statically consumes memory.
* Removed max number of duel at once.
* Updated duel modules for multi-thread and safer management.
* Remove various statically allocated tab.
* Removed duplicate code for npc_movenpc.
* Fix few warnings.
Thanks for suggestions from @anacondaqq.

src/map/map.cpp

@@ -2720,7 +2720,7 @@ int map_addmobtolist(unsigned short m, struct spawn_data *spawn)
 	if( i < MAX_MOB_LIST_PER_MAP )
 	{
 		map[m].moblist[i] = spawn;
-		return i;
+		return static_cast<int>(i);
 	}
 	return -1;
 }