Eagerly import the standard loop class when the hub is imported, preventing import lock issues under Py3. Fixes #687.

crash in a particular use cases. Fixes #237 and fixes #238.

Also clean up usage of hub._threadlocal, eliminating many try/except cases.

The particular crash seems to be in a corner-case usage (generally,
destroying a hub and/or loop seems to be advanced or rare usage), so I
feel pretty safe merging it into a release-track branch. The lifetime
management of the loop may not be totally ideal, but it solves the
issue. loop objects may now live longer (until the death of their
thread) if the hub was destroyed but the loop wasn't.

PyPy: Fix a corner case of an exception being raised by loop.handle_error during a callback that prevented other callbacks from running; this could ultimately lead to state corruption and *maybe* some crashes or leaks.

corecffi: Add a test for timer.again() and make sure timer.again() isn't subject to memory corruption that can crash the process.

Be more careful about the lifecycle management of watcher objects that may stop themselves. Fixes #676

Let GreenFileDescriptorIO inherit RawIOBase's read() method so that it handles negative/missing size reads appropriately. Fixes #675.

Always use the CountingHub, even when running leakchecks. Some tests, like test__issue607, depend on subclasses of ExpectedException not making it to the parent. The previous change to only use it sometimes (like in the past) broke those tests.

In the one example that had an import before gevent.monkey.patch_all(), move it up, as is recommended practice. Whitespace in comment.

Increase timeouts on appveyor as well as travis, and once again do so when running leak checks since that logic changed.

Make portforwarder and test__example_portforwarder.py behave the same on Windows and POSIX. Hopefully fixes the intermittant failures on Windows.

Fix test__makefile_ref on Windows using a test-time optional dependency on psutil. appveyor installs this dep.

Fix test__issues461_471 on Windows. Extensive comments about the differences in Windows signal handling inline.

I verified in a local VM that gevent's universal newline handling in subprocess matches the stdlibs (it's arguably broken). Update the tests for this case and mark them no longer failing

Make Popen.wait() raise the right exception on PY3 windows so that subprocess.call() doesn't hang if the process doesn't exit within the timeout.