* lisp/org-element.el (org-element-footnote-definition-parser):
Require 2 blank lines to separate footnote definition.
* lisp/org-footnote.el (org-footnote-at-definition-p): Require 2 blank
lines to separate footnote definition.
* doc/org.texi: Update documentation for footnotes.
* testing/lisp/test-org-element.el: Update tests.
* testing/lisp/test-org-footnote.el: Add tests.
Footnote definitions can still be separated with other footnote
definitions and headlines. This change allows to have multiple
paragraphs in a footnote definition without resorting to the "\par"
trick.