haxe.Timer.delay with haxe.MainLoop

```haxe
class Main {
public static function main():Void {
haxe.MainLoop.addThread(() -> trace("this prints"));
haxe.Timer.delay(() -> {
haxe.MainLoop.addThread(() -> trace("this does not print"));
}, 0);
}
}
```

Expected both to print, but only the first `trace` works. This is not a problem with logging – I verified by setting a value on the global object like so:

```haxe
class Main {
public static function main():Void {
js.Syntax.code("global.someTestValue = 0");
haxe.MainLoop.addThread(() -> js.Syntax.code("global.someTestValue = 1"));
haxe.Timer.delay(() -> {
haxe.MainLoop.addThread(() -> js.Syntax.code("global.someTestValue = 2"));
}, 0);
haxe.Timer.delay(() -> trace(js.Syntax.code("global.someTestValue")), 100);
}
}
```

(Outputs `1`.)

Compiled with `haxe -lib hxnodejs -main Main -js test.js` and executed with `node test.js`. Node version 8.5.0.