=====================
- Deal gracefully with greenlet switches that occur while deferred
deallocation of objects is happening using CPython's "trash can"
mechanism. Previously, if a large nested container held items that
switched greenlets during delayed deallocation, and that second
greenlet also invoked the trash can, CPython's internal state could
become corrupt. This was visible as an assertion error in debug
builds. Now, the relevant internal state is saved and restored
during greenlet switches. See also `gevent issue 1909
<https://github.com/gevent/gevent/issues/1909>`_.
- Rename the C API function ``PyGreenlet_GET_PARENT`` to
``PyGreenlet_GetParent`` for consistency. The old name remains
available as a deprecated alias.