Nightly Haxe/Hxcpp - Invalid constant when setting an abstract function param to a enum abstract value.

```hx
abstract class Foo {
abstract public function getData(type:Items = Sword):Void;
}

enum abstract Items(String) {
var Sword;
}
```
This code is considered fine on all targets besides hxcpp where we get the following error
```
[ERROR] src/Main.hx:8: characters 48-53
8 | abstract public function getData(type:Items = Sword):Void;
| ^^^^^
| Invalid constant : Sword
```
Error does not occur on haxe 4.3.7, on nightly haxe(5.0.0-preview.1+90a2a3c) js/neko/hl/eval all compile fine (https://try.haxe.org/#bf87b284)

Start with the provided Haxe snippet and reproduce it on the hxcpp target, comparing Haxe 4.3.7 with nightly 5.0.0-preview.1+90a2a3c and the js, neko, hl, and eval results linked in the issue. Done means the enum abstract value is accepted as the default parameter on hxcpp without the Invalid constant error.

Written by the indexing model from the issue text.