org-e-latex: Don't use mathrm in sub/superscripts with a single LaTeX command or entity

* contrib/lisp/org-e-latex.el (org-e-latex-subscript,
  org-e-latex-superscript): Don't use mathrm in sub/superscripts with
  a single LaTeX command or entity.
org-element: Allow links and export snippets in descriptions lists items tag

* contrib/lisp/org-element.el (org-element-object-restrictions): Allow
  links and export snippets in descriptions lists items tag.
org-element: Fix first section parsing

* contrib/lisp/org-element.el (org-element-current-element): Use a new
  special mode symbol to treat section before first headline
  differently.  In this case, its boundaries must be computed since it
  has not been limited by headline container.
(org-element-parse-elements): Use new special mode symbol.
org-e-ascii: Fix link description in empty section

* contrib/lisp/org-e-ascii.el (org-e-ascii-headline): Fix link
  description in empty section.
org-element: Rename a few internal functions

* contrib/lisp/org-element.el (org-element--parse-elements): Renamed
  from `org-element-parse-elements'.
(org-element--parse-objects): Renamed from `org-element-parse-objects'.
(org-element--get-next-object-candidates): Renamed from
`org-element-get-next-object-candidates'.
(org-element--interpret-affiliated-keywords): Renamed from
`org-element-interpret--affiliated-keywords'.
(org-element--current-element): Renamed from
`org-element-current-element'.
(org-element--collect-affiliated-keywords): Renamed from
`org-element-collect-affiliated-keywords'.
(org-element-center-block-parser, org-element-drawer-parser,
org-element-dynamic-block-parser,
org-element-footnote-definition-parser, org-element-inlinetask-parser,
org-element-plain-list-parser, org-element-quote-block-parser,
org-element-special-block-parser, org-element-comment-parser,
org-element-comment-block-parser, org-element-example-block-parser,
org-element-export-block-parser, org-element-fixed-width-parser,
org-element-horizontal-rule-parser,
org-element-latex-environment-parser, org-element-paragraph-parser,
org-element-src-block-parser, org-element-table-parser,
org-element-verse-block-parser, org-element-fill-paragraph,
org-element-context, org-element-at-point, org-element-interpret-data,
org-element-parse-secondary-string, org-element-parse-buffer): Apply
name change.
* contrib/lisp/org-export.el (org-export-get-buffer-attributes): Apply
  name change.
* testing/lisp/test-org-element.el: Update tests accordingly.
* testing/lisp/test-org-export.el: Update tests accordingly.
New alias `org-condition-case-unless-debug'.

* org-odt.el (org-odt-cleanup-xml-buffers): Use the new alias.

* org-compat.el: Alias `org-condition-case-unless-debug' to
`condition-case-unless-debug' or `condition-case-no-debug'.
org-odt.el: Replace `flet' with equivalent construct

* lisp/org-odt.el (org-odt-do-image-size): Replace `flet' with
equivalent construct.
org-compat.el: Augment earlier commit

* lisp/org-compat.el (org-condition-case-unless-debug): Alias
to `condition-case' when both `condition-case-no-debug' and
`condition-case-unless-debug' is unavailable.
Merge origin/maint
org-e-odt.el: Fix all compilation errors

Rearrange and rename for greater consistency and clarity.  More cleanups
will follow.
org-e-odt.el: Fix more compilation errors
Add autoload and a commands to export to temporary buffer in export back-ends

* contrib/lisp/org-e-ascii.el (org-e-ascii-export-as-ascii): New
  function.
(org-e-ascii-export-to-ascii): Now autoloaded.
* contrib/lisp/org-e-latex.el (org-e-latex-export-as-latex): New
  function.
(org-e-latex-export-to-pdf): Now autoloaded.
(org-e-latex--collect-errors): Renamed from
`org-e-latex-collect-errors'.
(org-e-latex-compile): Apply renaming.
* contrib/lisp/org-e-html.el (org-e-html-export-as-html): New
  function.
(org-e-html-export-to-html): Fix docstring.
* contrib/lisp/org-export.el (org-export-dispatch): Use new functions.
org-e-beamer: Small docstring changes

* contrib/lisp/org-e-beamer.el (org-e-beamer-export-as-latex,
  org-e-beamer-export-to-pdf): Small docstring changes.