bpo-18085: Update refcounts.dat. (GH-11247)

Fixed some errors in refcounts.dat, remove functions removed in
Python 3, and add more entries for documented functions. This will
add several automatically generated notes about return values.
(cherry picked from commit 83dd4e8)

Co-authored-by: Serhiy Storchaka <[email protected]>

Author: miss-islington