message: add capacity property.
diff: @@ -125,6 +125,8 @@ void swoole_channel_coro_init(int module_number TSRMLS_DC)
  {
  zend_register_class_alias("chan", swoole_channel_coro_class_entry_ptr);
  }
  +
  + zend_declare_property_long(swoole_channel_coro_class_entry_ptr, SW_STRL("capacity")-1, 0, ZEND_ACC_PUBLIC TSRMLS_CC);
  }
  static void channel_selector_clear(channel_selector *selector, swLinkedList_node *_node)
  @@ -416,6 +418,8 @@ static PHP_METHOD(swoole_channel_coro, __construct)
  }
  property->closed = 0;
  + zend_update_property_long(swoole_channel_coro_class_entry_ptr, getThis(), ZEND_STRL("capacity"), capacity TSRMLS_CC);
  +
  swoole_set_property(getThis(), CHANNEL_CORO_PROPERTY_INDEX, property);
  }
  