https://bugzilla.mozilla.org/show_bug.cgi?id=687400

There are cases where node equality is utilized that doesn't go through ```isSameNode()```, like in an ```indexOf()``` for example, so having a function for it isn't really useful. So, I'd say let's not have an extra function for this (even the W3C removed it from the DOM4 spec).

It would actually useful to have this, and all node equality going through this, so that you could for example wrap dom nodes (wrapping the same DOM node twice is not going to be strict equal - you'd have to unwrap the wrappers first), but that's not going to happen.