Update visibility system

*visibility updates and ai relocations processed simultaneously for each grid
  *these operations now are not synchronized for different grids
  *some changes into structure of visibility notifiers

--HG--
branch : trunk

src/game/Player.h

@@ -2180,8 +2180,10 @@ class Player : public Unit, public GridObject<Player>
         bool IsVisibleInGridForPlayer(Player const* pl) const;
         bool IsVisibleGloballyFor(Player* pl) const;
 
-        void UpdateVisibilityOf(WorldObject* target);
         void SendInitialVisiblePackets(Unit* target);
+        void UpdateObjectVisibility(bool forced = true);
+        void UpdateVisibilityForPlayer();
+        void UpdateVisibilityOf(WorldObject* target);
 
         template<class T>
             void UpdateVisibilityOf(T* target, UpdateData& data, std::set<Unit*>& visibleNow);