No error shown when using LegacyOctalEscapeSequence in string literal with Strict Mode

[kpreisser]

Hi, sorry if this is a duplicate.
I found that TypeScript is not reporting an error when using LegacyOctalEscapeSequence in a string literal when using Script Mode (according to ES2015 11.8.4):

TypeScript Version: 2.3.1-insiders.20170416

Code

function foo() {
    "use strict";    
    var s = "\04";
}

Expected behavior:
SyntaxError: Octal literals are not allowed in strict mode.

Actual behavior:
No error.

Thanks!

[mhegazy]

Duplicate of #396. PRs are welcomed for that one by the way.