Existing links have been updated to use the new reST role.  In some
files, I have also made cosmetic changes to the header.

This update includes new entries that apply to 2.7 too, mention of class
decorators, mention of nonlocal, notes about bytecode, markup fixes and
some rewrappings.  Future backports of changes should be slightly
easier.

No change was necessary to make the file build, contrary to cporting.rst
that uses markup like :c:func: that needs to be changed to :cfunc: in
2.7.  Future backports should be straightforward.

Georg added this role in our 3.2 doc tools and gave the greenlight for a
backport on python-dev.

This code is a simplified version of the 3.2 code; the version of Sphinx
used with Python 2.7 doesn’t have the function used to parse markup like
:role:`text to be displayed <text to be processed>` (I was persuaded it
was a standard reST construct, but it is actually a Sphinx innovation
that has to be supported explicitly in role code —I’ll be damned).  It
is thus not possible to write for example :source:`the NEWS file
<Misc/NEWS>`, but :source:`Misc/NEWS` will work.

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

to 8-bit strings.

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

Confirm that the prime example is actually correct.  We get so many complaints about a "buggy example" on docs@python, let us hope this cuts them in half at least.

Fix closes issue12698 - make the no_proxy environment variable handling a bit lenient (accomodate spaces in between the items)