Issue #18343: faulthandler.register() now keeps the previous signal handler
when the function is called twice, so faulthandler.unregister() restores
correctly the original signal handler.
Issue #17273: Clarify that pool methods can only be used by parent process.
Issue #14206: Clarify docs for Queue.join_cancel_thread().
Issue #17261: Ensure multiprocessing's proxies use proper address.
Closes #18312: 'make distclean' no longer deletes files in dot-directories.