bpo-39681: Fix C pickle regression with minimal file-like objects (GH-18592) (#18630)

Fix a regression where the C pickle module wouldn't allow unpickling from a
file-like object that doesn't expose a readinto() method.
(cherry picked from commit 9f37872e307734666a7169f7be6e3370d3068282)

Co-authored-by: Antoine Pitrou <antoine@python.org>

Co-authored-by: Antoine Pitrou <pitrou@free.fr>
3 files changed