Allows uppercase prefixes in JS number literals

[mariusschulz]

JavaScript allows both lowercase and uppercase prefixes in number literals:

const hex1 = 0x2A;      // 42
const hex2 = 0X2A;      // 42

const bin1 = 0b101010;  // 42
const bin2 = 0B101010;  // 42

const oct1 = 0o52;      // 42
const oct2 = 0O52;      // 42

This PR introduces support for 0X, 0B, and 0O.

[LeaVerou]

LGTM. Thanks!