This patch implements fully automatic creation of unique labels for
footnotes, which is also turned on as the default setting. The
automatic labels look like [fn:1], [fn:2], etc, using the first
available unused number.
The commit introduces a new variable, `org-footnote-auto-label' with a
number of different options ranging from no auto creation (prompting
the user for a label) to fully automatic creation.
Also, the commit introduces new #+STARTUP options that can be used to
select these settings on a per-file basis.
There was a bug with documents with more than one anonymous footnotes,
which would all end up to reference the first one only. The patch
fixes this problem.
Setting org-footnote-section to nil now causes definitions to be
inserted at the end of the current outline node, instead of into a
special node names "Footnotes".
Carsten Dominik