whatsnew: rewrite urllib, doctest, and poplib sections.

Also collapse redundant versionadded/versionchanged markup in
poplib.stls entry.
diff --git a/Doc/library/poplib.rst b/Doc/library/poplib.rst
index deb49fc..fa1db01 100644
--- a/Doc/library/poplib.rst
+++ b/Doc/library/poplib.rst
@@ -198,15 +198,13 @@
 
    *context* parameter is a :class:`ssl.SSLContext` object which allows
    bundling SSL configuration options, certificates and private keys into
-   a single (potentially long-lived) structure.
+   a single (potentially long-lived) structure.  This method supports
+   hostname checking via :attr:`SSLContext.check_hostname`
+   :attr:`SSLContext.check_hostname` and *Server Name Indicator* (see
+   :data:`~ssl.HAS_SNI`).
 
    .. versionadded:: 3.4
 
-   .. versionchanged:: 3.4
-      The method now supports hostname check with
-      :attr:`SSLContext.check_hostname` and *Server Name Indicator* (see
-      :data:`~ssl.HAS_SNI`).
-
 
 Instances of :class:`POP3_SSL` have no additional methods. The interface of this
 subclass is identical to its parent.