Issue #14252: Fix subprocess.Popen.terminate() to not raise an error under Windows when the child process has already exited.

Patch from Armin, test from me.

Some minidom code changed between 3.2 and 3.3, so to be sure to avoid
differenced in behavior I’m backporting these tests added by MvL.

Patch by Ralf Schmitt.

I assume that most users looking at this page are looking for a library
to process XML, not a low-level parser.  First proposed in #11379.

source generates a nifty link to the Mercurial web viewer.

Misc/COPYRIGHT was renamed twelve years ago to LICENSE and later copied
to the main docs, to which there is already a link.

Patch by Guilherme Gonçalves.

Issue #13491.

Issue #14159: Fix the len() of weak containers (WeakSet, WeakKeyDictionary, WeakValueDictionary) to return a better approximation when some objects are dead or dying.
Moreover, the implementation is now O(1) rather than O(n).
Thanks to Yury Selivanov for reporting.

#10713: Improve documentation for \b and \B and add a few tests.  Initial patch and tests by Martin Pool.