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/LiquidTile.h

@@ -42,7 +42,7 @@ public:
 private:
 	virtual Vec3 *getFlow(LevelSource *level, int x, int y, int z);
 public:
-	virtual void handleEntityInside(Level *level, int x, int y, int z, shared_ptr<Entity> e, Vec3 *current);
+	virtual void handleEntityInside(Level *level, int x, int y, int z, std::shared_ptr<Entity> e, Vec3 *current);
 	virtual int getTickDelay();
 	virtual int getLightColor(LevelSource *level, int x, int y, int z,  int tileId=-1);	// 4J - brought forward from 1.8.2
 	virtual float getBrightness(LevelSource *level, int x, int y, int z);