Works on Linux, doesn't work on Haiku. It appears xsltproc tries
to fetch the DTD and XSL stylesheets (which doesn't work, for some reason
it wasn't built with HTTP support, and I can't figure out why). Even
when telling it to use the preinstalled XSL & DTDs using --catalog,
it still tries to download the files...
DocBookCSS is a mostly-pure-CSS2 implementation of the DocBook standard.
Unlike DocBookXSL which relies on transforming the XML, it utilizes the
XML-styling features of modern web browsers to display the DocBook.
Its appearance still is a long way from the Haiku Book and Userguide, but
it looks (mostly) the same as the old DocBookXSL so we can stop using that.
Eventually we just need to make DocBookCSS use our styling.
