PollSelector.
This change is not really required in Python 3.4, since select.epoll.poll() now
rounds also correctly the timeout. But Guido van Rossum prefers to have exactly
the same selectors.py file in CPython and Tulip projects: "it's not harmful".
zero, instead of rounding towards zero. For example, a timeout of one
microsecond is now rounded to one millisecond, instead of being rounded to
zero.
Move also a test in test_epoll which was moved by my previous merge.