upgrade_data (Irc::Bot::Registry)

    # File lib/rbot/registry.rb, line 18
        def upgrade_data
          if File.exist?("#{@bot.botclass}/registry.db")
            log _("upgrading old-style (rbot 0.9.5 or earlier) plugin registry to new format")
            old = BDB::Hash.open("#{@bot.botclass}/registry.db", nil,
                                 "r+", 0600)
            new = BDB::CIBtree.open("#{@bot.botclass}/plugin_registry.db", nil,
                                    BDB::CREATE | BDB::EXCL,
                                    0600)
            old.each {|k,v|
              new[k] = v
            }
            old.close
            new.close
            File.rename("#{@bot.botclass}/registry.db", "#{@bot.botclass}/registry.db.old")
          end
        end