ox-texinfo: Fix heading text

* lisp/ox-texinfo.el (org-texinfo-headline): Do not sanitize heading
  text for sectioning command.

For example

  * This is ~code~

should be possibly exported as

  @chapter This is @code{code}

not

  @chapter This is @@code@{code@}
ox-texinfo: Fix appendix command

* lisp/ox-texinfo.el (org-texinfo-headline): Fix @appendix command.
ox-texinfo: Fix menus

* lisp/ox-texinfo.el (org-texinfo-make-menu): Change signature.
  Remove some intermediate functions.  Generate the full master menu
  when asked.
(org-texinfo--build-menu):  Use a simpler algorithm.
(org-texinfo--format-entries): Fix entries when both node and title
are different.
(org-texinfo--menu-entries): Renamed from `org-texinfo--generate-menu-list'.
(org-texinfo-headline): Move menu handling to next function.
(org-texinfo-section): Handle menu for current parent.
(org-texinfo--menu-headlines, org-texinfo--generate-detailed): Remove
functions.
(org-texinfo--normalize-headlines): New function.
ox-texinfo: Fix blank lines in output

* lisp/ox-texinfo.el (org-texinfo--normalize-headlines): Make sure
  a blank line always follows nodes.
ox-texinfo: Fix docstrings

* lisp/ox-texinfo.el (org-texinfo--sanitize-menu,
  org-texinfo--sanitize-content): Fix docstrings.
ox-texinfo: Fix node names

* lisp/ox-texinfo.el (org-texinfo--sanitize-node): "@", "{" and "}"
  characters are allowed in a node name.  So are "(" and ")" unless
  "(" starts the name and there is ")" somewhere in the name.  Also
  trim and collapse whitespace characters.  Renamed from
  `org-texinfo--sanitize-menu'.
(org-texinfo--get-node): Do not sanitize node names over zealously.
Ensure returned node names are unique.
(org-texinfo-headline): Only add @node command where it makes sense.
ox-texinfo: Remove unused internal functions

* lisp/ox-texinfo.el (org-texinfo--make-option-string,
  org-texinfo--sanitize-headline,
  org-texinfo--sanitize-headline-contents): Remove.
ox-texinfo: Fix a docstring

* lisp/ox-texinfo.el (org-texinfo-max-toc-depth): Fix docstring.
ox-texinfo: Tiny refactoring

* lisp/ox-texinfo.el (org-texinfo-info-process): Fix docstring.
(org-texinfo-compile): Do not check for impossible cases (e.g., if the
previous variable contains a function).
ox-texinfo: Remove left-over LaTeXism

* lisp/ox-texinfo.el (org-texinfo-headline): Remove LaTeXism (optional
  arguments within square brackets).
ox-texinfo: Remove `not-in-toc' case in headline export

* lisp/ox-texinfo.el (org-texinfo-headline): Remove `not-in-toc'
  special case for tags.

Check is useless for 2 reasons :

  1. there is no way to control @contents in the file header so
     sectioning name,

  2. menu entries provide their own title.  If it has to be handled,
     that should be elsewhere anyway.
org.texi: Document menus in Texinfo export

* doc/org.texi (Headings and sectioning structure): Document menus.
Merge branch 'maint'

Conflicts:
	doc/org.texi
	lisp/ox-texinfo.el
Silence byte-compiler
ox-texinfo: Remove wrong code comments

* lisp/ox-texinfo.el (org-texinfo-headline): Remove wrong code
  comments.
Merge branch 'maint'
ox-texinfo: Do not sanitize sectioning titles

* lisp/ox-texinfo.el (org-texinfo-headline): Do not sanitize
  sectioning titles.
ox-texinfo: Fix corner case when fixing a node name

* lisp/ox-texinfo.el (org-texinfo--sanitize-node): Handle
  " (not)allowed" case.
Merge branch 'maint'
lisp/org-agenda.el (org-agenda-refile): Documentation improvement

* lisp/org-agenda.el (org-agenda-refile): State explicitly that
  '(16) = C-u C-u and that '(64) = C-u C-u C-u.