Roundup supports Python versions 2.3 ff; this yields some compatibility
issues:

- the md5 and sha modules are deprecated as of Python 2.6,
  but the hashlib modules is not available before Python 2.5

- as of Python 2.6, the sets module is deprecated;
  the built-in set type should be used instead of sets.Set

This patch adds a compatibility layer to handle the Python version
issues; the modules in the anypy package provide only the functionality
which is in fact used by roundup.