I've changed the new functions to use METH_O, and I've copied the macros in from structseq.c, although these should really be exposed somewhere common, I imagine. Consequently, tests around usage of the structure are now in place, and I've added a test of unpickling an old time object to the test suite.

The reason for the changed ifdef is something I don't recall, so I've reverted that change as it doesn't seem to change the behaviour of the code when tested.
File Added: time-4.diff