[dom] Fix another NodeIterator removing step (#27)

This change makes it more consistent with the other rules. Also,
it is what the w3c test suite expects and how the browsers behave.

Here's a quick snippit to test:
```javascript
document.body.innerHTML = "<p>Efghijkl</p><p>Mnopqrst</p>";
var it = document.createNodeIterator(document);
while (it.nextNode());

var removed = document.body.children[1];
removed.parentNode.removeChild(removed);

console.info(it.referenceNode === document.body.children[0].lastChild);
console.info(it.pointerBeforeReferenceNode === false);
```
You can view, comment on, or merge this pull request online at:

  https://github.com/whatwg/dom/pull/27

-- Commit Summary --

  * Fix NodeIterator removing step

-- File Changes --

    M dom.bs (6)

-- Patch Links --

https://github.com/whatwg/dom/pull/27.patch
https://github.com/whatwg/dom/pull/27.diff

---
Reply to this email directly or view it on GitHub:
https://github.com/whatwg/dom/pull/27