org-export: Secondary strings are transcoded with `org-export-data'

org-export: Secondary strings are transcoded with `org-export-data'

* contrib/lisp/org-export.el (org-export-transcoder): New function.
(org-export-data): Also export secondary strings.  Refactored.
(org-export-secondary-string): Remove function.
(org-export-expand): Fix code indentation.
(org-export-expand-macro): Use `org-export-data' instead of
`org-export-secondary-string'.
* contrib/lisp/org-e-ascii.el (org-e-ascii--build-title,
  org-e-ascii--build-caption, org-e-ascii--list-listings,
  org-e-ascii--list-tables, org-e-ascii--describe-links,
  org-e-ascii-template--document-title, org-e-ascii-inlinetask,
  org-e-ascii-item, org-e-ascii-link, org-e-ascii-quote-section,
  org-e-ascii--table-cell-width): Use `org-export-data' instead of
  `org-export-secondary-string'.
* contrib/lisp/org-e-html.el (org-e-html-footnote-section,
org-e-html--caption/label-string, org-e-html-meta-info,
org-e-html-preamble, org-e-html-template,
org-e-html-format-headline--wrap, org-e-html-headline,
org-e-html-item, org-e-html-link): Use `org-export-data' instead of
`org-export-secondary-string'.
* contrib/lisp/org-e-latex.el (org-e-latex--caption/label-string,
  org-e-latex-template, org-e-latex-footnote-reference,
  org-e-latex-headline, org-e-latex-inlinetask, org-e-latex-item,
  org-e-latex-link, org-e-latex-src-block): Use `org-export-data'
  instead of `org-export-secondary-string'.
* contrib/lisp/org-e-odt.el (org-e-odt-format-preamble,
  org-e-odt-format-label, org-e-odt-update-meta-file,
  org-e-odt--caption/label-string, org-e-odt-footnote-def,
  org-e-odt-format-headline--wrap, org-e-odt-headline, org-e-odt-item,
  org-e-odt-latex-environment, org-e-odt-link, org-e-odt-src-block):
  Use `org-export-data' instead of `org-export-secondary-string'.