LONGMEADOW — Despite misgivings from the town’s lawyers and some dog owners, Town Meeting on Tuesday approved a bylaw that deems “dangerous” any dog that attacks without provocation.Voters approved the bylaw 70-48, as the clock neared 11 p.m., almost four hours after the May 12 meeting had begun. Less than one-fifth of the 644 residents who had voted on fiber-optic network funding remained in the gymnasium at Longmeadow High School for the dog v…