Alright, but as a side note I still think that having `EventConfig` as an optional parameter could be useful because we can leverage `EventConfig::avoidMethod()` to configure libevent in order to optionally blacklist `epoll` as a backend when running on linux:

```php
$cfg = new EventConfig();
$cfg->avoidMethod("epoll");

$loop = new React\EventLoop\ExtEventLoop($cfg);
```

Anyway let's leave this to a later PR for discussion, there's enough stuff already happening here and I'd prefer to merge only the `nextTick()` functionality with its changes so that more devs can start to play with it and do tests.