message: default options for kernel
diff: /* Micro version is omitted if it's 0 */
  #define WAMPCC_NAME_VERSION "wampcc 1.0"
  -namespace wampcc {
  +namespace wampcc
  +{
  class io_loop;
  class event_loop;
  @@ -40,10 +41,12 @@ int micro_version();
  */
  struct logger
  {
  - enum Level {eError = 0x02,
  + enum Level {
  + eError = 0x02,
  eWarn = 0x04,
  eInfo = 0x10,
  - eDebug = 0x40};
  + eDebug = 0x40,
  + };
  // generate bit masks to represent levels that shall be logged
  static int levels_all() { return -1; }
  @@ -51,7 +54,8 @@ struct logger
  static int levels_upto(Level l);
  std::function<bool(Level)> wants_level;
  - std::function<void(Level, const std::string&, const char* file, int ln)> write;
  + std::function<void(Level, const std::string&, const char* file, int ln)>
  + write;
  /** create a logger for stdout or stderr */
  static logger stdlog(std::ostream&, int level_mask, bool inc_file_line);
  @@ -78,8 +82,7 @@ struct config
  std::function<void()> event_loop_end_fn;
  config()
  - : socket_buffer_max_size_bytes(65536),
  - socket_max_pending_write_bytes(65536)
  + : socket_buffer_max_size_bytes(65536), socket_max_pending_write_bytes(65536)
  {
  }
  };
  @@ -90,7 +93,7 @@ struct config
  class kernel
  {
  public:
  - kernel(config, logger nlog);
  + kernel(config = {}, logger nlog = logger::nolog());
  ~kernel();
  kernel(const kernel&) = delete;
  