ox-texinfo: Fix error with wide @direntry

* lisp/ox-texinfo.el (org-texinfo-template): Properly pad @direntry
  description.
ox-texinfo: Fix comments handling

* lisp/ox-texinfo.el (texinfo): Make sure comments are ignored.
(org-texinfo-comment, org-texinfo-comment-block): Remove functions.

This is consistent with all other back-ends, which ignore any comment.
ox-texinfo: Fix docstrings

* lisp/ox-texinfo.el (org-texinfo-node-description-column,
  org-texinfo-format-drawer-function): Fix docstrings.
ox-texinfo: Properly handle subauthors and email

* lisp/ox-texinfo.el (org-texinfo-template): Fix multi-line
  subauthors.  Correctly add email, when provided.  Check if author
  info is wanted first.

This patch also removes AUTHOR variable since it's up to the user to
set it or not, through a class or a header keyword.
ox-texinfo: Handle documents without copying information

* lisp/ox-texinfo.el (org-texinfo-template): Check if copying data is
  not nil before using it.
ox-texinfo: Check options before inserting TOC

* lisp/ox-texinfo.el (org-texinfo-template): Make sure table of
  contents are allowed before inserting them.
ox-texinfo: Fix multi-line subtitles

* lisp/ox-texinfo.el (org-texinfo-template): Fix multi-line subtitles.
ox-texinfo: Remove spurious blank lines in output

* lisp/ox-texinfo.el (org-texinfo-template): Remove spurious blank
  lines in output.  Refactor code.
ox-texinfo: Fix `org-texinfo-classes'

* lisp/ox-texinfo.el (org-texinfo-classes): Change default value.
  Update docstring.
(org-texinfo-template): Insert header string from current class after
"@settitle" command.  Always provide "\input texinfo" at the beginning
of the output.

Header string in the class was inserted before "@setfilename".
Texinfo ignores anything between "\input texinfo" and that command,
making any value besides the default one useless.
ox-texinfo: Do not hardcode "Manual" in top node

* lisp/ox-texinfo.el (org-texinfo-template): Do not hardcode "Manual"
  in top node.
ox: Provide output file name, if any, to back-ends

* lisp/ox.el (org-export-to-file): Provide output file name in
  communication channel, through :output-file property.

This change is needed to fix back-ends needing this information during
the process, e.g., `texinfo'.
ox-texinfo: Fix @setfilename command

* lisp/ox-texinfo.el (texinfo): Do not provide a default value for
  @setfilename value.
(org-texinfo-filename): Remove variable.
(org-texinfo-template): Correctly find value for @setfilename command.
If none is possible, do not provide the command at all.
ox-texinfo: Fix table export

* lisp/ox-texinfo.el (org-texinfo-table): Remove reference to
  "verbatim" attribute.  Handle table.el tables.  Tiny refactoring.
(org-texinfo-table--org-table, org-texinfo-table--table.el-table):
Remove functions.
(org-texinfo-table-column-widths): Indent code correctly.  Ignore
special column, if any.  Add a comment about the limitation on the
width computation.
(org-texinfo-table-row): Small refactoring.
ox-texinfo: Fix verse block export

* lisp/ox-texinfo.el (org-texinfo-verse-block): Generate somewhat
  meaningful Texinfo code instead of LaTeX.
ox-texinfo: Appendix has precedence over regular sectionning

* lisp/ox-texinfo.el (org-texinfo-headline): Always obey to
  a non-nil :APPENDIX: property.  Small refactoring.
ox-texinfo: Allow to set a different title for hard copy

* lisp/ox-texinfo.el (texinfo): Provide new export property.
(org-texinfo-template): Use dedicated title for hard copy, when
available.
ox-texinfo: Fix plain lists export

* lisp/ox-texinfo.el (org-texinfo-plain-list): Fix format string.
  Small refactoring.
ox-texinfo: Code comments clean-up
org.texi: Document Texinfo export back-end
Merge branch 'maint'

Conflicts:
	doc/org.texi
	lisp/ox-texinfo.el