Issue #27056: Optimize pickle.load() and pickle.loads(), up to 10% faster to
deserialize a lot of small objects.

* Replace PyUnicode_RPartition() with PyUnicode_FindChar() and
  PyUnicode_Substring() to avoid the creation of a temporary tuple.
* Use PyUnicode_FromFormat() to build a string and avoid the single_dot ('.')
  singleton

Thanks Serhiy Storchaka for your review.

These added a path attribute to pathlib.Path objects, and docs.
Instead, we're going to use PEP 519.

(Starting in the 3.4 branch and merging forward from there since that's what I did originally.)

Issue #27057: Fix os.set_inheritable() on Android, ioctl() is blocked by
SELinux and fails with EACCESS. The function now falls back to fcntl().

Patch written by Michał Bednarski.

Removes versioning from py.exe launcher installer and ensures that old launchers are replaced by newer ones.

Documentation updates by Martin Panter.

issue27045 - Use backslash in windows path to script file.