[eval] enum abstract with @:native

Compiling the following test with `haxe --run Test` fails with the error:
`Field index for fromString not found on prototype MyType`

```haxe
class Test {
static function main()
{
var myType = MyType.ONE;
trace(myType);

myType = "two";
trace(myType);
}
}

@:native("MyType")
enum abstract MyType(String) to String {
public var ONE = "one";
public var TWO = "two";

@:from static public function fromString(str:String):MyType {
return cast str;
}
}
```

Removing `@:native` or renaming the value inside it seems to fix it.

Tested and working at least on js. neko, java, cpp, hl.

haxe 4 preview 5 (latest from git)