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/DiggingEnchantment.h

@@ -10,5 +10,5 @@ public:
 	virtual int getMinCost(int level);
 	virtual int getMaxCost(int level);
 	virtual int getMaxLevel();
-	virtual bool canEnchant(shared_ptr<ItemInstance> item);
+	virtual bool canEnchant(std::shared_ptr<ItemInstance> item);
 };