ARLINGTON, Texas, July 6 : Portugal forward Cristiano Ronaldo's final World Cup ended with a Spanish sting in the tail, courtesy of Mikel Merino's last-gasp winner that earned a 1-0 round-of-16 win on Monday, but he was unwilling to make a hasty call on his international future.Ronaldo told reporters in the mixed zone that Spain enjoyed "a bit of luck" to score through substitute Merino in the dying moments of a match he felt could have swung either way."I'm sad to be leaving the World Cup like this," he said. "I gave it my all. I did my best and I'm leaving with a clear conscience. It was my last World Cup, yes, but I'll now have time to reflect and be with my family. I won't be making any rash decisions."The 41-year-old stopped short of confirming whether he had played his final game for