for-of with `const` variable

[Isiah Meadows]

I was toying around with for-of loops in Node 4.0, and I ran into the
following problem:

```
$ node
> for (let i of [1, 2, 3]) console.log(i)
1
2
3
undefined
> for (const i of [1, 2, 3]) console.log(i)
1
1
1
undefined
```

That second loop is rather surprising. Is that the correct behavior
(in which I need to file an ESLint bug), or is this a V8 bug?

-- 
Isiah Meadows