Agreed about the compatibility. It's there from pkgutil, where to be
honest, it's even less necessary, as simplegeneric was for internal use
only, there. I'm certainly not aware of any backward compatibility
requirements for functools.

Assuming nobody speaks up to the contrary, I'll rip out the
compatibility bits in the next version of the patch.

I'm unsure about the non-decorator version of register. I can imagine
use cases for it - consider pprint, for example, where you might want to
register str as the overload for your particular type. But it's not a
big deal either way.