***Steve Martin’s breakout comedy*** A homeless mentally-challenged man (Steve Martin) shares his amusing tale of rags-to-riches-to-hobo with flashbacks. Catlin Adams plays a stunt rider at a carnival who has the hots for Navin (Martin) while Bernadette Peters plays a more important woman in his life. “The Jerk” (1979) has several laugh-out-loud scenes like the eventual confrontation between Patty (Catlin) and Marie (Peters), but there are also some flat, overlong parts, like when Navin departs the mansion in the last act. “Forrest Gump” (1994) was obviously inspired by “The Jerk” and made a…