Check if `ToLength` is implemented correctly

[mathiasbynens]

As reported by @medikoo here: 0e41b31#commitcomment-6175170

[medikoo]

Other issues I see:

• Array.from as per spec, doesn't produce sparse arrays any more. So e.g. this test should fail, as now expected value is { 0: undefined, length: 1 }
• There's no support for iterators. To have it fixed it actually demands taking Symbol shim inside, so not easy, if you'd like to keep it as light deps free function. However you can fix internally resolution of strings, as I did -> https://github.com/medikoo/es5-ext/blob/master/array/from/shim.js#L65-L85

[ljharb]

This is now implemented correctly.