BANGKOK — The historic Bui Chu Cathedral in Vietnam, a 135-year-old church considered by many an architectural gem, is being demolished to make room for a bigger cathedral despite last-ditch efforts to save it. By Wednesday, workers had removed tiles from the floor and dismantled much of the roof of the cathedral, which is in Nam Dinh Province, about two hours south of Hanoi. A high fence has been erected around the building, and demolition will most likely be completed by early next month.