partially support non-enumerability

[Raynos]

https://gist.github.com/1672142

Since we emulate defineProperty and Object.keys we can keep a record of any non-enumerable properties defined through our defineProperty shim and then reference them in Object.keys.

This means that non-enumerable works for Object.keys but fails with for..in

Is this of value or do we just not want to support non-enumerability?

[domenic]

I think introducing an inconsistency between Object.keys and for-in is not a good price to pay. Doing so breaks an invariant of the language.

[bryanforbes]

I agree with @DomenicDenicola on this. As a generic shim, we can't introduce an inconsistency like this.