Issue #17926: Fix dbm.__contains__ on 64-bit big-endian machines.
Issue #17928: Fix test_structmembers on 64-bit big-endian machines.

(_testcapi isn't Py_ssize_t-clean, the "s#" code should use an int for length)
Fix NEWS order
#16523: improve attrgetter/itemgetter/methodcaller documentation.
Issue #17656: Skip test_extract_unicode_filenames if the FS encoding
doesn't support non-ASCII filenames.