Patch by Zooko O'Whielacronx.

Issue #14166: Pickler objects now have an optional `dispatch_table` attribute which allows to set custom per-pickler reduction functions.
Patch by sbt.

This makes the C implementation more aligned with the Python implementation.
Also added some tests to ensure that Element is now a type and that it can
be subclassed.

Add checks in PyUnicode_WriteChar() and convert PyUnicode_New() assertion to a
test raising a Python exception.

  string.  Patch by Guilherme Gonçalves.

Patch by Guilherme Gonçalves.

verbose arguments from all threading classes and functions.

Add a private API to convert an int or float to a C timespec structure.

Issue #13491.

Issue #13491.

Issue #14159: Fix the len() of weak containers (WeakSet, WeakKeyDictionary, WeakValueDictionary) to return a better approximation when some objects are dead or dying.
Moreover, the implementation is now O(1) rather than O(n).
Thanks to Yury Selivanov for reporting.

Issue #14159: Fix the len() of weak containers (WeakSet, WeakKeyDictionary, WeakValueDictionary) to return a better approximation when some objects are dead or dying.
Moreover, the implementation is now O(1) rather than O(n).
Thanks to Yury Selivanov for reporting.