Require unreleased Autoconf for fixed AC_PROG_INSTALL. * m4/init.m4 (AM_INIT_AUTOMAKE): Bump AC_PREREQ to 2.61-341, regenerate files. * configure.ac: Also require Autoconf 2.61-341, to catch failure early and provide a sensible error message. Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>