The southern French city of Marseille has been rocked by a violent confrontation between two drug gangs in which the alleged perpetrators and victims are getting younger and younger. Public Prosecutor Nicolas Bessone on Monday spoke of “extraordinary, unprecedented violence” after a 15-year-old was stabbed and burned alive, while a 14-year-old alleged hit man is accused of shooting a cab driver in the head simply because he refused to stop. Investigators believe an ongoing fight between the “DZ Mafia” and the “Clan des Blacks” over a lucrative drug sales point in the city as the trigger for th…