Inventory: Send dirty lists where appropriate (#8742)

This change reduces the amount of sent data towards clients. Inventory lists that are already known to the player are skipped, saving quite some data over time.

Raises protocol version to 38 to ensure correct backwards-compatible code.

src/network/clientpackethandler.cpp

@@ -333,7 +333,7 @@ void Client::handleCommand_Inventory(NetworkPacket* pkt)
 
 	player->inventory.deSerialize(is);
 
-	m_inventory_updated = true;
+	m_update_wielded_item = true;
 
 	delete m_inventory_from_server;
 	m_inventory_from_server = new Inventory(player->inventory);