org-element: Function mapped through org-element-map accepts only one argument

org-element: Function mapped through org-element-map accepts only one argument

* contrib/lisp/org-element.el (org-element-map): Remove use of an
  alternate communication channel.  Function is now called with only
  one argument.
* contrib/lisp/org-export.el (org-export-collect-tree-properties):
(org-export-collect-headline-numbering, org-export--selected-trees,
org-export-collect-footnote-definitions,
org-export-footnote-first-reference-p,
org-export-get-footnote-number, org-export-resolve-fuzzy-link,
org-export-resolve-id-link, org-export-resolve-ref-link,
org-export-resolve-coderef, org-export-get-ordinal,
org-export-get-loc, org-export-collect-headlines): Apply changes.
* EXPERIMENTAL/org-e-ascii.el (org-e-ascii--unique-links): Apply
  changes.
* EXPERIMENTAL/org-e-publish.el (org-e-publish-collect-index): Apply
  changes.