ChakraCore rounds too nicely for `toFixed` and `toPrecision`

Input:

```js
1.1.toFixed(20);
1.1.toPrecision(21)
```

These should both output `"1.10000000000000008882"`, and do so in other engines. See the loop in step 8 of https://tc39.github.io/ecma262/#sec-number.prototype.tofixed -- The algorithm is different (simpler) than Number.prototype.toString.