Unexpected behavior for ~/\b/g.split() on some targets

Followup for #9601.

___

```haxe
function main() {
trace(~/\b/g.split("Test"));
}
```

Targets seem to disagree there:

- `[,T,e,s,t]` for eval
- `[,T,est]` for neko, cpp and hl
- `[,Test,]` for js, swf, python, php, lua, jvm and cs

We should check if eval, cpp and hl can be aligned with the other targets. Not sure anybody wants to touch neko at this point.