HONG KONG -- Hong Kong authorities on Tuesday said they plan to amend a film censorship law to forbid screenings of movies deemed contrary to national security.The proposed changes to Hong Kong’s Film Censorship Ordinance would step up censorship of movies in the semi-autonomous city, expanding an ongoing crackdown on political dissent that has led to the closure of various pro-democracy organizations and the arrests of dozens of activists.The amendments would require a censor to determine