gnulib-tool.py: Follow gnulib-tool changes, part 35.

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.