Integrate "autoupdate" in autoreconf job
autoupdate is a Perl script which updates syntax of configure.ac to the current version of Autoconf (in our case Autoconf from the base image, that is version 2.69 from Debian 10 "buster").
Running autoupdate as part of the autoreconf CI job ensures configure.ac being in line with Autoconf syntax best practices.
Changes in fa6cd603 were made by autoupdate, except for the win32utils/Configure change, and the m4_define([bind_PKG_VERSION]... change, which is needed for the BIND version being set correctly in the ARMv9 PDF (reStructuredText -> \LaTeX -> PDF).
configure.ac autoupdate changes on v9_11 seems too extensive to be integrated.