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

Moved symlink support into its own module. Ported can_symlink from Python 3.2, skipping symlink test when it cannot be invoked (such as when the symlink privilege is not present).

Extracted Windows directory detection from NullImporter.__init__. This greatly simplifies the code and fixes issue6727.

Patch from Armin, test from me.

Closes #14158: We now track test_support.TESTFN cleanup, and test_mailbox uses shutil.rmtree for simpler code.

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.

Initial patch by Johannes Vogel. Issue #13491.

Issue #14159: Fix the len() of weak sets 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.