Add support for Python 3.12 and 3.13.

[hodgestar]

Currently tests with Python 3.12 fail because of the usual Python AST changes.

[FelixSchwarz]

Interestingly the test suite for Genshi 0.7.7 works in Fedore for 3.12 and 3.13 so it has to be one of the recent changes for 0.7.8 which triggers the test failure. Maybe it was broken already in 3.12 and nobody noticed but for the record, this is the only patch Fedora ships for Genshi: https://src.fedoraproject.org/rpms/python-genshi/blob/rawhide/f/python-genshi-use-default-test-loader.patch

[hodgestar]

The master branch now supports Python 3.12 (fixed in #77).

@FelixSchwarz I also applied the Fedora patch.

[hodgestar]

Support for Python 3.13 added in #81.

[mgorny]

Thanks a lot!