Patch by A. Jesse Jiryu Davis

Patch by Susumu Koshiba.

Fix a "gcc -pendatic" warning.

Fix a "gcc -pedantic" warning on "buffer += n" because buffer type is void*.

Issue #26839: On Linux, os.urandom() now calls getrandom() with GRND_NONBLOCK
to fall back on reading /dev/urandom if the urandom entropy pool is not
initialized yet. Patch written by Colm Buckley.

Patch by SilentGhost.

- "See also" links to the new docs are now provided in the legacy pages
- links to setuptools documentation have been updated

(original patch by Susan Sun)

Based on patch by Xiang Zhang.

Patch by Xiang Zhang.

Patch by Xiang Zhang.