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/MobSpawnerTile.h

@@ -9,7 +9,7 @@ class MobSpawnerTile : public EntityTile
 protected:
 	MobSpawnerTile(int id);
 public:
-    virtual shared_ptr<TileEntity> newTileEntity(Level *level);
+    virtual std::shared_ptr<TileEntity> newTileEntity(Level *level);
 	virtual int getResource(int data, Random *random, int playerBonusLevel);
     virtual int getResourceCount(Random *random);
     virtual bool isSolidRender(bool isServerLevel = false);