main/autoconf: upgrade to 2.72
https://github.com/autotools-mirror/autoconf/blob/v2.72/NEWS
license
updated to GPL-3.0-or-later WITH Autoconf-exception-3.0
based on https://github.com/autotools-mirror/autoconf/commit/675a0c95df
https://github.com/autotools-mirror/autoconf/blob/v2.72/NEWS
license
updated to GPL-3.0-or-later WITH Autoconf-exception-3.0
based on https://github.com/autotools-mirror/autoconf/commit/675a0c95df