I need to copy this file in another test too, so I moved the support
code to distutils.tests.support and improved it:

- don’t skip when run from the Lib/distutils/tests directory
- use proper skip machinery instead of custom print/return/test suite
  fiddling.

I added a link from the term “virtual subclass” to the glossary entry
for ABCs but this was not enough, now the glossary briefly defines
“virtual” and links to the abc module doc which contains more mentions
of virtual subclasses.

Suggested by Terry J. Reedy.

``code`` markup is enough to mark command-line fragments or to talk
about a character.  ``'c'`` is still used for actual Python string
objects.  I did a similar change in optparse.rst in r86521.

I’ve also ported two minor changes from the 3.3 version of the file
(removing an unnecessary module name in a class directive, adding a
comma).

I made the doc for the compat alias BadZipfile shorter and used a
directive to document deprecation.

I figured there was no point of talking about zipfile.error (“the old
name” that’s older than the other old name BadZipfile) in the 3.x docs
so I just removed it.

time to spawn.

resources (FD/zombie) when killed at the wrong time.

#12266: Fix str.capitalize() to correctly uppercase/lowercase titlecased and cased non-letter characters.

normalization is different between unicode builds, so use a new non-BMP char and add normalization test

This fixes the use of Unicode identifiers outside the BMP in narrow builds.

Changes to crlf originally by Victor Stinner for 3.3, copied to lfcr by
me.  Manually tested.

The line about the test suite will still get printed for changes in
Tools for example, which aren’t covered by the test suite, but it’s not
a big deal IMO.