Stung by the crash of the housing market, some struggling homeowners are using a little known but increasingly popular provision of the bankruptcy code to eliminate second mortgages and avoid foreclosure. Statistics are hard to come by, but bankruptcy lawyers say the provision has been used effectively on hundreds, if not thousands, of cases in the Bay Area during the past two years. “It’s a big thing in our valley,” said James “Ike” Shulman, a San Jose bankruptcy lawyer. “But it’s not widely known.”