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/PickaxeItem.h

@@ -9,12 +9,12 @@ class PickaxeItem : public DiggerItem
 private:
 	static TileArray *diggables;
 
-public: // 
+public: //
 	static void staticCtor();
 
 	PickaxeItem(int id, const Tier *tier);
 
 public:
 	virtual bool canDestroySpecial(Tile *tile);
-	virtual float getDestroySpeed(shared_ptr<ItemInstance> itemInstance, Tile *tile);	// 4J - brought forward from 1.2.3
+	virtual float getDestroySpeed(std::shared_ptr<ItemInstance> itemInstance, Tile *tile);	// 4J - brought forward from 1.2.3
 };