Issue #18756: os.urandom() now uses a lazily-opened persistent file descriptor, so as to avoid using many file descriptors when run in parallel from multiple threads.
Use the recent support.HOSTv6 addition.
Use INADDR_BROADCAST instead of hard-coded value (it's part of POSIX and
already appears without #ifdef a couple lines above).
Fix XMLPullParser documentation to say "non-blocking" instead of "asynchronous".
The latter is more ambiguous.

Related to issue #17741
Merge.
Close #18780: %-formatting now prints value for int subclasses with %d, %i, and %u codes.
Temporary disable tests cleanup (issue 11798).
Issue #18780: code cleanup.
Issue #18489: Add complete, gui-free tests for idlelib.SearchEngine.
Patch import and initialization in SearchEngine to make testing easier.
Improve docstrings, especially to clarify the double role of 'ok' parameters.
Original patch by Phil Webster.
Merge from 3.3 #18489 Search Engine tests
Issue #12037: Fix test_email for desktop Windows.
Issue #12037: Fix test_email for desktop Windows.