* There were leaks if Py_tp_bases is used more than once or if some call is
failed before setting tp_bases.
* There was a crash if the bases argument or the Py_tp_bases slot is not a tuple.
* The documentation was not accurate.
(cherry picked from commit 1db76394ea79030aa4ed5349c950f6c6da51450f)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>