shared_ptr -> std::shared_ptr

This is one of the first commits in a plan to remove all `using namespace std;` lines in the entire codebase as it is considered anti-pattern today.

Minecraft.World/StoneSlabTile.h

@@ -35,5 +35,5 @@ public:
 	virtual unsigned int getDescriptionId(int iData = -1);
 	virtual int getAuxName(int auxValue);
 protected:
-	virtual shared_ptr<ItemInstance> getSilkTouchItemInstance(int data);
+	virtual std::shared_ptr<ItemInstance> getSilkTouchItemInstance(int data);
 };