Rebecca Davis editorHong Kong on Wednesday formally banned films that are deemed to “threaten national security” with an amendment to beef up its existing film censorship law, the latest move to tighten the grip on artistic and speech freedoms in the country.The city’s legislative council — in which there are no opposing forces — amended the Film Censorship Bill by a show of hands to give movie censors the task of vetting content for violations of a draconian national security written and