PyPy not getting an int from microsecond.to_integral()

Hi,

Dunno if you're interested but PyPy 1.9 is expecting an int from microsecond.to_integral() which apparently it isn't getting, according to the test failures. I've added a crude switch as a workaround for my own purposes (checking that tests for rdflib plugins pass under PyPy).

Cheers,

Graham