2.6.8: Mar 23 2004:
   - First step of the cleanup of the serialization code and APIs
   - XML Schemas: mixed content (Adam Dickmeiss), QName handling fixes (Adam
    Dickmeiss), anyURI for "" (John Belmonte)
   - Python: Canonicalization C14N support added (Anthony Carrico)
   - xmlDocCopyNode() extension (William)
   - Relax-NG: fix when processing XInclude results (William), external
    reference in interleave (William), missing error on <choice>
    failure (William), memory leak in schemas datatype facets.
   - xmlWriter: patch for better DTD support (Alfred Mickautsch)
   - bug fixes: xmlXPathLangFunction memory leak (Mike Hommey and William
    Brack), no ID errors if using HTML_PARSE_NOERROR, xmlcatalog fallbacks to
    URI on SYSTEM lookup failure, XInclude parse flags inheritance (William),
    XInclude and XPointer fixes for entities (William), XML parser bug
    reported by Holger Rauch, nanohttp fd leak (William),  regexps char
    groups '-' handling (William), dictionnary reference counting problems,
    do not close stderr. 
   - performance patches from Petr Pajas
   - Documentation fixes: XML_CATALOG_FILES in man pages (Mike Hommey)
   - compilation and portability fixes: --without-valid, catalog cleanups
    (Peter Breitenlohner), MingW patch (Roland Schwingel), cross-compilation
    to Windows (Christophe de Vienne),  --with-html-dir fixup (Julio Merino
    Vidal), Windows build (Eric Zurcher)