bpo-38294: Add list of no-longer-escaped chars to re.escape documentation. (GH-16442)

Prior to 3.7, re.escape escaped many characters that don't have
special meaning in Python, but that use to require escaping in other
tools and languages. This commit aims to make it clear which characters
were, but are no longer escaped.
(cherry picked from commit 15ae75d660)

Co-authored-by: Ricardo Bánffy <rbanffy@gmail.com>

Doc/library/re.rst

@@ -931,8 +931,8 @@ form.
    This is useful if you want to match an arbitrary literal string that may
    have regular expression metacharacters in it.  For example::
 
-      >>> print(re.escape('python.exe'))
-      python\.exe
+      >>> print(re.escape('http://www.python.org'))
+      http://www\.python\.org
 
       >>> legal_chars = string.ascii_lowercase + string.digits + "!#$%&'*+-.^_`|~:"
       >>> print('[%s]+' % re.escape(legal_chars))
@@ -955,7 +955,9 @@ form.
 
    .. versionchanged:: 3.7
       Only characters that can have special meaning in a regular expression
-      are escaped.
+      are escaped. As a result, ``'!'``, ``'"'``, ``'%'``, ``"'"``, ``','``,
+      ``'/'``, ``':'``, ``';'``, ``'<'``, ``'='``, ``'>'``, ``'@'``, and
+      ``"`"`` are no longer escaped.
 
 
 .. function:: purge()

Doc/tools/susp-ignored.csv

@@ -354,3 +354,4 @@ whatsnew/changelog,,::,default::BytesWarning
 whatsnew/changelog,,::,default::DeprecationWarning
 library/importlib.metadata,,:main,"EntryPoint(name='wheel', value='wheel.cli:main', group='console_scripts')"
 library/importlib.metadata,,`,loading the metadata for packages for the indicated ``context``.
+library/re,,`,"`"

Misc/NEWS.d/next/Documentation/2019-09-27-23-37-41.bpo-38294.go_jFf.rst

@@ -0,0 +1 @@
+Add list of no-longer-escaped chars to re.escape documentation