Bob Einstein, whose 50-year career as a comedy writer and performer ranged from “The Smothers Brothers Comedy Hour” to Larry David’s “Curb Your Enthusiasm,” has died. He was 76. Part of a show-business family, Einstein’s comedic resume included playing the fictional daredevil Super Dave Osborne, and, most recently, the dour Marty Funkhouser on David’s HBO series. His brother, writer, director and