This is ugly but makes things work again. I intend to clean this up once
we have a better attribute API
* Recognize mw:WikiLink, mw:SimpleWikiLink, mw:ExtLink,
mw:NumberedExtLink and mw:UrlLink
* Support is incomplete because we can't get to the annotation text with
the current API
* Preserve all unhandled attributes rather than special-casing data-mw
* Update remaining code using data-mw (sHref and stx extraction) to
account for the data-mw -> data-rt rename
* Update tests accordingly
Change-Id: Ia13d3008a6d4cdc8828f9acda5aa797566bc597f