org-odt.el: Consider short captions not as org text but as plain text

org-odt.el: Consider short captions not as org text but as plain text

* lisp/org-lparse.el (org-lparse-insert-org-table): Consider
short caption as plain text and not as org text.
* lisp/org-odt.el (org-export-odt-format-formula)
(org-export-odt-format-image): ditto.

Fixes earlier checkin.  See
http://lists.gnu.org/archive/html/emacs-orgmode/2012-03/msg01212.html

Handling of short captions is only a convenience feature.

From within LibreOffice one can always create an "unprotected"
editable index and later manually delete unwanted index entries (for
example, delete uncaptioned entries which are given automatic names)
or modify existing entries (for example, fix long captions to their
short versions).