- Footnotes separator rather than headline to get around i18n
- Warn on footnote redefinition
- Do not export footnote definitions at point of definition, only in the
footnote section.
- Do not automatically exclude Footnotes section to get around possibly hiding
other content of such a section - and i18n.
The user has the choice of explicitly hiding the section via a :noexport:
tag.
and some other refactoring
