message: use the server character_set when the character_set is not set.
diff: @@ -504,6 +504,12 @@ static int mysql_handshake(mysql_connector *connector, char *buf, int len)
  memcpy(tmp, &value, sizeof(value));
  tmp += 4;
  + //use the server character_set when the character_set is not set.
  + if (connector->character_set == 0)
  + {
  + connector->character_set = request.character_set;
  + }
  +
  //character set
  *tmp = connector->character_set;
  tmp += 1;
  @@ -841,9 +847,10 @@ static PHP_METHOD(swoole_mysql, connect)
  RETURN_FALSE;
  }
  }
  + //use the server default charset.
  else
  {
  - connector->character_set = SW_MYSQL_DEFAULT_CHARSET;
  + connector->character_set = 0;
  }
  swClient *cli = emalloc(sizeof(swClient));
  