Make typecasting methods *really* safe and get rid of redundant typeId/Typemask checks, thanks Zor and Machiavelli for help

--HG--
branch : trunk

src/server/game/Entities/Item/Item.cpp

@@ -257,6 +257,16 @@ Item::Item()
     m_paidExtendedCost = 0;
 }
 
+inline Bag* Item::ToBag()
+{
+    return dynamic_cast<Bag*>(this);
+}
+
+inline const Bag* Item::ToBag() const
+{
+    return dynamic_cast<const Bag*>(this);
+}
+
 bool Item::Create(uint32 guidlow, uint32 itemid, Player const* owner)
 {
     Object::_Create(guidlow, 0, HIGHGUID_ITEM);

src/server/game/Entities/Item/Item.h

@@ -347,6 +347,9 @@ class Item : public Object
 
         void BuildUpdate(UpdateDataMapType&);
 
+        Bag* ToBag();
+        const Bag* ToBag() const;
+
     private:
         std::string m_text;
         uint8 m_slot;