properly, and use this to skip test_multiprocessing on platforms
where sem_open raises a signal. This should fix some FreeBSD buildbot
failures for test_multiprocessing.
PyString_FromFormat which has an independent implementation, and uses "%zd".
This makes a difference on win64, where printf needs "%Id" to display
64bit values. For example, queue.__repr__ was incorrect.
Reviewed by Martin von Loewis.