Rest from Array doesn't work properly

When creating an Array and populating it with push(), the Rest from it doesn't work correct - it adds null value at the end. The bug in --java and --jvm:

```Haxe
import haxe.Rest;

class Main {
static public function main() {
var a:Array = new Array();
a.push(1);
a.push(2);
a.push(3);
trace(a, a.length); // [1,2,3], 3
var r = Rest.of(a);
trace(r, r.length); // [1,2,3,null], 4
}
}
```

```
-cp src
-main Main
--each

--java bin/java
--next

--jvm bin/jvm/main.jar
--next

--interp
```

Start with the haxe.Rest.of(a) path used by the --java and --jvm targets, reproducing the sample with the commands in the issue. Compare those results with --interp; done means Rest contains exactly the three pushed values and reports length 3 without the trailing null.

索引モデルが issue の本文から書いたものです。