An upstate graduate student was charged yesterday with stabbing a beloved anthropology professor to death. Saudi national Abdulsalam Al-Zahrani, 46, was held without bail for the murder of Binghamton University professor Richard Antoun, 77, an expert on comparative religion, authorities said. Al-Zahrani, a cultural-anthropology grad student, allegedly pulled out a six-inch kitchen knife and stabbed Antoun four times in the chest in the professor's campus office Friday.