Owen Gleiberman Chief Film Critic The first thing to say about Alex Gibney’s “In Restless Dreams: The Music of Paul Simon” is that it’s three-and-a-half hours long. Normally I wouldn’t lead with that daunting fact, especially since the film is mostly marvelous: a documentary that every Paul Simon fan on earth should want to see and experience. But will they? I raise the issue only because “In Restless Dreams” has come into the Toronto Film Festival without a distributor, and let’s just be honest: The 209-minute running time, when you hear about it, doesn’t exactly sound…user-friendly.