add_sigint_handler (Autotest)

    # File lib/autotest.rb, line 273
      def add_sigint_handler
        trap 'INT' do
          if self.interrupted then
            self.wants_to_quit = true
          else
            unless hook :interrupt then
              puts "Interrupt a second time to quit"
              self.interrupted = true
              Kernel.sleep 1.5
            end
            raise Interrupt, nil # let the run loop catch it
          end
        end
      end