many texi2html warnings for lilypond-snippets.texi

[Werner LEMBERG]

Compiling the documentation in current git with `make web', texi2html
(CVS version from 2009-01-09) produces zillion warnings like this:

  texi2html --I=/home/wl/lilypond/out/xref-maps \
            --I=. \
            --I=./out-www \
            --output=out-www/lilypond-snippets/ \
            --prefix=index \
            --split=section \
            --init-file=/home/wl/lilypond/lilypond-texi2html.init \
            out-www/lilypond-snippets.texi

  *** Duplicate node found:
      Adding beams
      (in out-www/expressive-marks.texi l. 13 in @lydoctitle)
  *** Duplicate node found:
      Changing text and spanner styles for text dynamics
      (in out-www/expressive-marks.texi l. 407 in @lydoctitle)
  *** Duplicate node found:
      Printing metronome and rehearsal marks below the staff
      (in out-www/expressive-marks.texi l. 1635 in @lydoctitle)

  ...

  ** node_next `slurs'
               for `Adding beams' not found
  ** node_prev `ties etc. when using tuplet and non-tuplet rythms.'
               for `Adding beams' not found
  ** No node following `Adding ambitus per voice' in menu,
     but `Ambitus with multiple voices' follows in sectionning

  ...


     Werner