gnulib-tool.py: Follow gnulib-tool changes, part 35. Follow gnulib-tool change 2023-05-28 Bruno Haible <bruno@clisp.org> warnings, manywarnings: Assume autoconf >= 2.64. * pygnulib/GLConfig.py (GLConfig.default, GLConfig.getAutoconfVersion) (GLConfig.setAutoconfVersion, resetAutoconfVersion): Set required Autoconf version to 2.64. * pygnulib/GLError.py (GLError.__init__, GLError.__repr__): Likewise. * pygnulib/GLImport.py (GLImport.__init__): Likewise. * pygnulib/constants.py (DEFAULT_AUTOCONF_MINVERSION): Likewise. * pygnulib/main.py: Likewise.