docbook bugfix

[Jose Abilio Oliveira Matos]

Hi,
  I send a patch against the latest cvs source to fix a bug
where if the some nested list were in the end of the document
their tags weren't correctly closed.
  Even if this bug is very rare, since the lists should be the
last element in the document, it happens and so it should be
fixed.

  BTW, using lyx I have nested till the 6th nest level, more
than latex is able to deal with. I didn't try more if someone
wants to try this tells us the result. :)
-- 
José

jamatos-990928.patch.gz