Make the various iterators' "setstate" sliently and consistently clip the
index.  This avoids the possibility of setting an iterator to an invalid
state.
Make the various iterators' "setstate" sliently and consistently clip the
index.  This avoids the possibility of setting an iterator to an invalid
state.
asyncio: Synchronize with Tulip

* Issue #159: Fix windows_utils.socketpair()

  - Use "127.0.0.1" (IPv4) or "::1" (IPv6) host instead of "localhost", because
    "localhost" may be a different IP address
  - Reject also invalid arguments: only AF_INET/AF_INET6 with SOCK_STREAM (and
    proto=0) are supported

* Reject add/remove reader/writer when event loop is closed.
* Fix ResourceWarning warnings
asyncio, Tulip issue 157: Improve test_events.py, avoid run_briefly() which is
not reliable