For DocBook XML compatibility, don't use SGML empty tags (</>) anymore,
replace by the full tag name. Add a warning option to catch future
occurrences.
Alexander Lakhin, Jürgen Purtz
Block elements with verbatim formatting (literallayout, programlisting,
screen, synopsis) should be aligned at column 0 independent of the surrounding
SGML, because whitespace is significant, and indenting them creates erratic
whitespace in the output. The CSS stylesheets already take care of indenting
the output.
Assorted markup improvements to go along with it.