Rather than referring to the external xorg.css stylesheet, embed the content
of the file in the html output produced. This is accomplished by using
version 1.10 of xorg-xhtml.xsl.

This makes the whole html docs tree much more relocatable.
In addition, it eliminates xorg.css as a runtime file which makes
xorg-sgml-doctools a build time only package.

Signed-off-by: Gaetan Nadon <nadon@memsize.(none)>