CAIRO (Reuters) - Saudi Arabia’s Crown Prince Mohammed bin Salman met Coptic Pope Tawadros II at Cairo’s largest Coptic cathedral on Monday in what state media said was an unprecedented visit by an official from the conservative Muslim kingdom. The visit was part of a three-day stay in Egypt for Prince Mohammed, his first public trip abroad since he became heir apparent last year. He will head for Britain and the United States later this month. Cairo and Riyadh have strengthened ties in recent years and Egypt has received billions of dollars in aid from its rich Gulf Arab ally....