* XSLT stylesheet included from other stylesheet are not among dependencies
   (if you modify html.common.xsl) then the html output won't be rebuilt
 * Support for man pages
 * Support for embedded css stylesheets in generated HTML documents
 * There is an issue with .d files, they are not sometimes regenerated when
   one of the files included gets changed to a non-existent file and back
   (maybe it happens only when you run make clean html)