[3.12] Add 'The Python 2.3 Method Resolution Order' (pythonGH-116435)

(cherry picked from commit 7d0be7a)

Co-authored-by: Hugo van Kemenade <[email protected]>

Author: hugovk

Doc/glossary.rst

@@ -799,8 +799,7 @@ Glossary
 
    method resolution order
       Method Resolution Order is the order in which base classes are searched
-      for a member during lookup. See `The Python 2.3 Method Resolution Order
-      <https://www.python.org/download/releases/2.3/mro/>`_ for details of the
+      for a member during lookup. See :ref:`python_2.3_mro` for details of the
       algorithm used by the Python interpreter since the 2.3 release.
 
    module

Doc/howto/index.rst

@@ -32,4 +32,7 @@ Currently, the HOWTOs are:
    perf_profiling.rst
    annotations.rst
    isolating-extensions.rst
+   timerfd.rst
+   timerfd.rst
+   mro.rst