cesanta/v7 — pull request #19 by mmikulicic (2014-12-04 17:28:25+00:00)
Title: Fix `substr` and add `substring`

See:

- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substring
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substr

Tested with:

- node -e "console.log('hi there'.substr(3, 2))"
- node -e "console.log('hi there'.substring(3, 5))"