`parseInt(08)` should work in sloppy mode?

### Input Code

``` js
parseInt(08);
```
### Babel Configuration (.babelrc, package.json, cli command)

``` js
{
  "sourceType": "script" // so that it's not strict
}
```
### Expected Behavior

Should evaluate to `8`.
### Current Behavior

Throws SyntaxError.
### Your Environment

| software | version |
| --- | --- |
| Babel | 6.17 |
