Disable auto-pickling to work around...

Disable auto-pickling to work around https://github.com/cython/cython/issues/1786. We don't want to allow that in a point-release of gevent anyway.

src/gevent/_semaphore.pxd

+# cython: auto_pickle=False
 cdef class Semaphore:
     cdef public int counter
     cdef readonly object _links

src/gevent/_semaphore.py

+# cython: auto_pickle=False
 import sys
 from gevent.hub import get_hub, getcurrent
 from gevent.timeout import Timeout

src/gevent/ares.pyx

 # Copyright (c) 2011-2012 Denis Bilenko. See LICENSE for details.
+# Automatic pickling of cdef classes was added in 0.26. Unfortunately it
+# seems to be buggy (at least for the `result` class) and produces code that
+# can't compile ("local variable 'result' referenced before assignment").
+# See https://github.com/cython/cython/issues/1786
+# cython: auto_pickle=False
 cimport cares
 import sys
 from python cimport *

src/gevent/libev/corecext.ppyx

 # Copyright (c) 2009-2012 Denis Bilenko. See LICENSE for details.
 # This directive, supported in Cython 0.24+, causes sources files to be
 # much smaller and thus cythonpp.py to be slightly faster. But it does make
-# debugging more difficult.
-# cython: emit_code_comments=False
+# debugging more difficult. Auto-pickling was added in 0.26, and that's a new feature
+# that we don't need or want to allow in a gevent point release.
+# cython: emit_code_comments=False, auto_pickle=False
 cimport cython
 cimport libev
 # Note this is not the standard cython 'cpython' (which has a backwards compat alias of 'python')