Support for client version 7.6

Tell me if there are parts which I should change.

- Not everything is tested yet, feel free to report bugs in 7.6
- the data send in between login opcode and account data might not be
correct, but I could not find any documents showing the right protocol
yet
- Hotkeys working

src/client/game.h

@@ -158,6 +158,7 @@ public:
     void useWith(const ItemPtr& fromThing, const ThingPtr& toThing);
     void useInventoryItem(int itemId);
     void useInventoryItemWith(int itemId, const ThingPtr& toThing);
+    ItemPtr findItemInContainers(uint itemId, int subType);
 
     // container related
     int open(const ItemPtr& item, const ContainerPtr& previousContainer);