[libstdc++,doc] update a link in doc/xml/manual/policy_data_structures_biblio.xml

[Gerald Pfeifer]

Both the protocol (https) and the local part of the URL changed;
updates thusly and committed.

Gerald

2018-09-24  Gerald Pfeifer  <gerald@pfeifer.com>

	* doc/xml/manual/policy_data_structures_biblio.xml: Update link
	to "Priority Queues and the STL".
 
Index: doc/xml/manual/policy_data_structures_biblio.xml
===================================================================
--- doc/xml/manual/policy_data_structures_biblio.xml	(revision 264517)
+++ doc/xml/manual/policy_data_structures_biblio.xml	(working copy)
@@ -1139,7 +1139,7 @@
     <biblioentry xml:id="biblio.nelson96stlpq">
       <title>
 	<link xmlns:xlink="http://www.w3.org/1999/xlink"
-	      xlink:href="http://marknelson.us/1996/01/01/priority-queues/">Priority Queues and the STL
+	      xlink:href="https://marknelson.us/posts/1996/01/01/priority-queues.html">Priority Queues and the STL
 	</link>
       </title>
       <date>