Enumerate spec violations

[littledan]

I think it would be useful to enumerate spec violations and see which ones we can and can't fix over time.

[rricard]

@nicolo-ribaudo we should do a session where we go through the spec and do that

[mhofman]

I believe the current polyfill implementation interns the first 0 value and later uses that when it encounters another +0 or -0.

const nz = #[-0];
log(Object.is(#[+0][0], +0)); // false, should be true