Added data-xrefstyle to XREF specifications.
Added data-xrefstyle to XREF specifications.

gitenberg-dev/HTMLBook,oreillymedia/HTMLBook,wastemobile/HTMLBook,wastemobile/HTMLBook,macmillanpublishers/HTMLBook,mushroomgithub/HTMLBook,mushroomgithub/HTMLBook,oreillymedia/HTMLBook,gitenberg-dev/HTMLBook,macmillanpublishers/HTMLBook,mushroomgithub/HTMLBook,oreillymedia/HTMLBook,gitenberg-dev/HTMLBook,macmillanpublishers/HTMLBook