Documentation DTD

Anyone mind if we bump the DTD version to Docbook 4.2?

This consists on all users who wish to build docs on installing the 4.2
DTD set, and updating some depreciated tags within the sgml files.

comment -> remark
docinfo -> appendixinfo, chapterinfo, bookinfo, etc.


What it buys is a number of useful tags, SVGs and probably more
importantly for the future, xsl and fop support which will probably be
important in the future.  OpenJade hasn't had a new release in quite a
long time -- not to say work isn't needed.

Yes, after updating docs to the newer DTD I intend to make them XML
compliant to ensure they work with v5 of docbook in the future.