Fix typos found by codespell in docs, docstrings, and comments.
Fixes for the following files were in post-3.6 code and not backported:
Lib/ctypes/_aix.py (new), Lib/test/test_concurrent_futures.py,
Modules/_asynciomodule.c, Modules/_pickle.c, Objects/obmalloc.c.

(cherry picked from commit c3d9508f)