maint: resync most files from upstream

maint: resync most files from upstream

The files in lib/Autom4te/ are intentionally not synced at this point,
since automake commit v1.11-2114-g2d671e1 "perl refactor: use modern
semantics of 'open'":
<http://lists.gnu.org/archive/html/automake-patches/2012-03/msg00111.html>
would require wider adaptation of our scripts to the new XFile API, and
also exposes some latent bugs in autoconf where we use raw 'open' instead
of XFile::open.  We'll take care of that in a later patches (maybe).

* build-aux/announce-gen: Resync via 'make fetch'.
* build-aux/config.guess: Likewise.
* build-aux/config.sub: Likewise.
* build-aux/gendocs.sh: Likewise.
* build-aux/gitlog-to-changelog: Likewise.
* build-aux/gnupload: Likewise.
* build-aux/texinfo.tex: Likewise.
* doc/make-stds.texi: Likewise.
* doc/standards.texi: Likewise.
* maint.mk: Likewise.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>