[BUG] [ODT] Subtree export gives wrong footnote style

[Christian Moe <christian.moe@hf.uio.no>]

Hi,

The new ODT exporter sometimes, but not always fails to put footnotes in
Footnote style as expected. They are left in Text Body, which is wrong
(and surprisingly difficult to fix in LibreOffice).

After a bit of trial and failure, it seems the error depends on the
scope of export: 

Exporting the whole buffer gives correct footnote style.

Exporting a subtree only fails to give the correct style -- *unless* the
footnote is included in the subtree. In the example below, I actually
get a mix of stylesm depending on whether the footnote is defined in the
exported section or outside it. Org-mode is clearly able to find both
footnotes, and recognize them as footnotes, so I'm baffled at the
different styling.

---------Begin example

#+TITLE: Test ODT footnote style
#+OPTIONS: num:nil toc:nil

* This is a heading

This is a bit of body text.[fn:1] It has footnotes.[fn:2]

[fn:1] This is a footnote I have placed in the same section that I am
exporting. It is in Footnote style (correct).

* Footnotes

[fn:2] This is a footnote in a footnote section. When I export the
section above as a subtree, this footnote is in Text Body
(wrong). When I export the whole document, it's in Footnote style
(correct).

---------End example

Yours,
Christian