Fix overflowing test on Windows

The test assumed incorrectly that Python’s sys.maxsize is the size of
the C long type.  In particular, this is not true on 64 bit Windows.
3 jobs for master in 7 minutes and 15 seconds (queued for 1 second)
latest
Status Name Job ID Coverage
  Test
passed python2 #148919

00:00:22

passed python3 #148920

00:00:34

 
  Deploy
passed create conda dev package #148921

00:06:41