If the name Shecky Greene does not ring a bell, you might not be the target audience for this new documentary. But there was once a time when someone with this unlikely name roamed the Earth, and this film chronicles the prehistoric, pre-TV age in which such comedians flourished. The doc proposes New York’s Catskill Mountains as the cradle of a couple of generations of comedy, and it is hard to argue with the assertion. A vast parade of stand-up comics, mostly Jewish, passed through the vacation resorts of the Borscht Belt, as the circuit was called. During the mid-20th century, the Catskills hummed with holiday-makers seeking escape from New York, in search of all-you-can-eat buffets and the latest variation on the mother-in-law joke.