Incorrectly claiming functions are unused

[Wilfred]

/* jshint strict:false, unused:true, undef:false */
(function() {
    function main() {
        helperFunc();

    }

    window.main = main;

    function helperFunc() {
    }
})();

Produces the following error:

$ jshint ~/scratch/badapp.js 
/home/wilfred/scratch/badapp.js: line 10, col 14, 'helperFunc' is defined but never used.

1 error
$ jshint --version
jshint v2.6.3

[ghost]

👍 The last version this has worked correctly is 2.5.

[lukeapage]

duplicate/related to #2191

[lukeapage]

Fixed in the next release (after 2.8.0)