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/TemptGoal.cpp

@@ -31,7 +31,7 @@ bool TemptGoal::canUse()
 	player = weak_ptr<Player>(mob->level->getNearestPlayer(mob->shared_from_this(), 10));
 	if (player.lock() == NULL) return false;
 	mob->setDespawnProtected();		// If we've got a nearby player, then consider this mob as something we'd miss if it despawned
-	shared_ptr<ItemInstance> item = player.lock()->getSelectedItem();
+	std::shared_ptr<ItemInstance> item = player.lock()->getSelectedItem();
 	if (item == NULL) return false;
 	if (item->id != itemId) return false;
 	return true;