Drop support for 'configure.in' as the Autoconf input file The autoconf input should be named 'configure.ac' instead. The use of 'configure.in' has been deprecated in Autoconf since at least the 2.13 -> 2.50 transition, and future Autoconf versions (starting with 2.70 probably) will start to warn about it at runtime. Automake has been warning about it since the 1.13 release. This change is basically a backport of commit 'v1.12-325-g927d4cb', from Automake-NG. * lib/Automake/Configure_ac.pm (find_configure_ac): Don't look for 'configure.in' if 'configure.ac' is not found. (require_configure_ac): On failure, don't tell that "'configure.ac' or 'configure.in' is required", but just that "'configure.ac' is required". * automake.in (@common_sometimes): Don't list 'configure.in'. (scan_autoconf_files): Adjust heading comments. * NEWS: Update. * t/help.sh: Adjust. * t/configure.sh: Remove as obsolete. * t/list-of-tests.mk: Adjust.