RIJEKA, Croatia — Fighting fatigue but determined to carry on, Pope John Paul II wrapped up his 100th foreign pilgrimage Monday amid nagging questions about how long he can endure the rigors of the road. A trip to Mongolia in August is up in the air, but the 83-year-old pope sets out again in less than two weeks for Bosnia-Herzegovina, where he won’t be able to count on the adoring crowds he found in his grueling five-day tour of Croatia.