Update Muse XML schema.

Update Muse XML schema.

* examples/muse.rnc: Allow nested list items.  Update header.  Provide
  history.  We'll call this v0.3 of the schema.

* lisp/muse-xml-common.el: Update header.
  (muse-xml-markup-table): Fix table generation when attributes are not
  specified.

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Files to commit:
   lisp/muse-wiki.el
   lisp/muse-http.el
   lisp/muse-html.el
   lisp/muse.el
   lisp/muse-docbook.el
   lisp/muse-convert.el
   lisp/muse-colors.el
   lisp/muse-book.el
   lisp/muse-texinfo.el
   lisp/muse-publish.el
   lisp/muse-project.el
   lisp/muse-poem.el
   lisp/muse-mode.el
   experimental/muse-message.el
   lisp/muse-latex.el
   lisp/muse-journal.el
   lisp/muse-regexps.el
   experimental/muse-mathml.el
   lisp/muse-latex2png.el
   examples/mwolson/stylesheets/screen.css
   examples/mwolson/stylesheets/print.css
   examples/mwolson/stylesheets/common.css
   examples/mwolson/stylesheets/common.css
   examples/mwolson/stylesheets/blog.css
   examples/mwolson/stylesheets/blog.css
   lisp/muse-registry.el
   examples/muse.rnc
   examples/mwolson/muse-init.el
   AUTHORS
   lisp/muse-backlink.el
   debian/copyright
   lisp/muse-xml-common.el
   muse.texi
   lisp/muse-protocols.el
   experimental/muse-cite.el
   README
   lisp/muse-xml.el
   lisp/muse-blosxom.el
   lisp/muse-groff.el
   COPYING
   .arch-ids/COPYING.id

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git-archimport-id: mwolson@gnu.org--2006/muse--main--1.0--patch-60