JSONObject do support octal

[sberyozkin]

JSONObject do support octal and hexadecimal numbers (0777, 0xABCD), but JSON.org states that JSON does not support them, and ES5 goes as far as forbidding them http://es5.github.com/#B.1
Since extra leading zeros might creep in the input, I think it's better to ignore them than return a completely different number from the one intended (how often does one use octal nowadays? except in chmod parameters, maybe...)