Update FlxUIInputText.hx

* Added `params` when broadcasting the events.

In needed to get a specific `FlxUIInputText` in my `FlxUIScene::getEvent()` so I added a param on it:
```haxe
var input = new FlxUIInputText(0, 0, 200);
input.params = ["my very specific field"];
```

But for some reason FlxUIInputText didn't support params? It's useful
Merge pull request #58 from AndreiRegiani/patch-2

Params for FlxUIInputText.hx