MDL-44798 editor_atto: Backport a fix for HTML5Shiv

This is a backport of the Rangy workaround for a bug in HTML5Shiv, which
breaks document.createElement by returning nodes which have parent nodes.

HTML5Shiv refuses to fix this bug so Rangy has had to work around it.

For more information see:
* https://code.google.com/p/rangy/issues/detail?id=104; and
* https://github.com/aFarkas/html5shiv/issues/64.