- Issue #15234: For BerkelyDB and Sqlite, only add the found library and
  include directories if they aren't already being searched. This avoids
  an explicit runtime library dependency.
Fixes for KFreeBSD and the Hurd:

- Issue #21274: Define PATH_MAX for GNU/Hurd in Python/pythonrun.c.

- Issue #21276: posixmodule: Don't define USE_XATTRS on KFreeBSD and the Hurd.

- Issue #21275: Fix a socket test on KFreeBSD.
- Issue #21285: Refactor and fix curses configure check to always search
  in a ncursesw directory.
fix ref count annotations on sphinx >= 1.2.1 (closes #21286)
correct len signature in docstring (closes #21294)