readline: use native `codePointAt`
readline: use native `codePointAt`

Semver: patch
PR-URL: https://github.com/iojs/io.js/pull/825
Reviewed-By: Chris Dickinson <38a75c4c4f5646d63b752460df745c5b937b7e58@gmail.com>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node