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/PlayerInputPacket.h

@@ -31,6 +31,6 @@ public:
 	bool isSneaking();
 
 public:
-	static shared_ptr<Packet> create() { return shared_ptr<Packet>(new PlayerInputPacket()); }
+	static std::shared_ptr<Packet> create() { return std::shared_ptr<Packet>(new PlayerInputPacket()); }
 	virtual int getId() { return 27; }
 };