Coming from a 25-year-old debut filmmaker, the spirited, naturalistic coming-of-age comedy “Everybody Wants Some!!” would be enticing. But for Richard Linklater, a 55-year-old director with five Academy Award nominations to his credit, this first-novelish piece feels like a step back and a step down. A fulsomely, aggressively modest no-star picture, it’s a plotless, pointless two-hour hangout...