merge branch 'maint'

* upstream/maint:
  maint: post-release administrivia
  version 3.5.3
  news: update for 3.5.3
  yacc.c: make sure we properly propagated the user's number for error
  diagnostics: don't crash because of repeated definitions of error
  style: initialize some struct members
  diagnostics: beware of zero-width characters
  diagnostics: be sure to close the styling when lines are too short
  muscles: fix incorrect decoding of $
  code: be robust to reference with invalid tags
  build: fix typo
  doc: update recommandation for libtextstyle
  style: comment changes
  examples: use consistently the GFDL header for readmes
  style: remove useless declarations
  typo: succesful -> successful
  README: point to tests/bison, and document --trace
  gnulib: update
  maint: post-release administrivia

TODO

@@ -305,13 +305,8 @@ It would be a very nice source of inspiration for the other languages.
 Valentin Tolmer is working on this.
 
 ** YYERRCODE
-Defined to 256, but not used, not documented.  Probably the token
-number for the error token, which POSIX wants to be 256, but which
-Bison might renumber if the user used number 256.  Keep fix and doc?
-Throw away?
-
-Also, why don't we output the token name of the error token in the
-output?  It is explicitly skipped:
+Why don't we output the token name of the error token in the output?  It is
+explicitly skipped:
 
       /* Skip error token and tokens without identifier.  */
       if (sym != errtoken && id)