message: change default max-irreversible-block-age to unlimited
diff: @@ -412,8 +412,8 @@ void producer_plugin::set_program_options(
  ("pause-on-startup,x", boost::program_options::bool_switch()->notifier([this](bool p){my->_pause_production = p;}), "Start this node in a state where production is paused")
  ("max-transaction-time", bpo::value<int32_t>()->default_value(30),
  "Limits the maximum time (in milliseconds) that is allowed a pushed transaction's code to execute before being considered invalid")
  - ("max-irreversible-block-age", bpo::value<int32_t>()->default_value( 30 * 60 ),
  - "Limits the maximum age (in seconds) of the DPOS Irreversible Block for a chain this node will produce blocks on")
  + ("max-irreversible-block-age", bpo::value<int32_t>()->default_value( -1 ),
  + "Limits the maximum age (in seconds) of the DPOS Irreversible Block for a chain this node will produce blocks on (use negative value to indicate unlimited)")
  ("producer-name,p", boost::program_options::value<vector<string>>()->composing()->multitoken(),
  "ID of producer controlled by this node (e.g. inita; may specify multiple times)")
  ("private-key", boost::program_options::value<vector<string>>()->composing()->multitoken()->default_value({fc::json::to_string(private_key_default)},
  