IN Hollywood, it used to be you had to produce before you produced. But it's not the case anymore with a crop of teenage and young adult stars who are moving onto the backlots of Tinseltown with production companies. Selena Gomez, 19, has a development deal. Gomez is just one of several young actors - including 23-year-old Zac Efron and 19-year-old Taylor Lautner - producing their own movies. These actors have their own production companies, but they're not necessarily calling the shots in Hollywood - yet. According to one veteran producer, for many young actors, production deals provide a way to pay a manager or family member who's been an informal adviser without having to take money out of the actor's salary. New York Post