Log Message:
Update to 6.7

Changelog:
6.7 (23 September 2019)
* Language:
  . support of index subentries and sub-subentries with @subentry
  . new commands @seeentry and @seealso in index entries
  . no need to wrap Top node in @ifnottex - omitted automatically when
    processed with TeX
  . UTF-8 is the default input encoding

* texi2any
  . for HTML output, mark index nodes in menus and tables of contents
    with the 'rel' attribute of the 'a' tag.
  . TOP_NODE_UP is now only used in HTML if TOP_NODE_UP_URL is set.
    Also TOP_NODE_UP should now be formatted in the output format.
    In HTML TOP_NODE_UP should be suitable for inclusion in HTML
    element attributes, so for instance should not contain elements.
  . support of noderename.cnf files has been removed
  . INPUT_PERL_ENCODING, INPUT_ENCODING_NAME, NODE_FILE_EXTENSION,
    NODE_FILENAMES, SHORTEXTN and TOP_NODE_FILE removed as customization
    variables.
  . TOP_NODE_FILE_TARGET now contains the extension.
  . error messages translated when the XS parser module is in use

* texi2dvi
  . unconditionally run in --batch mode, i.e. without stopping if there
    is a TeX error
  . keep on going after a TeX error if the index files changed
  . with --tidy (or --build-dir), avoid reading index files from previous
    runs where --tidy was not used

* info
  . for a tree search (with M-/), '}' and '{' work as well as 'M-}' and
    'M-{' to go through the results

* Distribution:
  . Several obsolete portability checks removed
  . gettext 0.20.1, automake 1.16.1

6.6 (16 February 2019)
* Language:
  . new commands @&, @ampchar{}
  . @cropmarks command removed
  . @ctrl is no longer recognised (it was a way to insert literal
    control characters in Info files, but deprecated since the
    time of Texinfo version 2)
  . \usebracesinindexestrue is no longer recommended for using braces in
    index entries, and has been a no-op for some time

* texi2any
  . extension modules fixed to work with the "thread-safe locales" of
    Perl 5.28 and newer
  . some code changed to stop warnings being given by newer versions of Perl
  . for HTML output, use `id' to define link targets instead of the `name'
    attribute on <a>
  . A native-code implementation of the Texinfo parser has been included
    on an experimental basis, which makes texi2any a lot faster.  Set the
    `TEXINFO_XS_PARSER' environment variable to 1 to use.
  . changes to HTML output:
     . omit colon after node name in menus by default (use
       `MENU_ENTRY_COLON' to add it back)
     . no special CSS for commands like @smallexample
     . new customization variable `SECTION_NAME_IN_TITLE' to use the
       section name as the document <title>
     . use section names instead of node names in generated menus
  . pass on flags set with -D to TeX
  . useless static libraries are not installed
  . the newline after an @insertcopying is not output
  . warning given for @multitable prototypes not in braces
  . @indent and @noindent are not allowed inside the arguments to
    commands where they are not meaningful
  . @quote-arg and @allow-recursion are not recognised (these two used
    to be recognised by makeinfo in macro definitions but were never
    implemented in texinfo.tex)
  . `FIX_TEXINFO' removed as a customization variable
  . do not recognise or warn about obsolete customization variables

* info
  . debugging output with -x is not diverted to a separate infodebug file

* Development:
  . switch from Subversion to git
     - https://savannah.gnu.org/git/?group=texinfo
  . automake 1.16