switch to xml docbook

["Matthias Clasen" <Matthias Clasen poet de>]

Yesterday I switched glib and gobject HEAD to --output-format=xml. And 
despite Owens concerns, widget.gnome.org
seems to cope with docbook xml, thus you can see the result on 
http://developer.gnome.org/doc/API/2.0/glib/index.html
One thing you'll probably note immediately is that somehow the move to xml 
ate the short descriptions in the toc. 
I'll fix that soon.

Matthias