libstdc++: Fix broken link to SGI STL FAQ

The previous URL to an entry in the wayback machine now redirects to a
page saying "SGI.com Tech Archive Resources now retired" so use an older
entry from the archive.

	* doc/xml/faq.xml: Use working link for SGI STL FAQ.
	* doc/html/*: Regenerate.

libstdc++-v3/ChangeLog

+2020-05-04  Jonathan Wakely  <jwakely@redhat.com>
+
+	* doc/xml/faq.xml: Use working link for SGI STL FAQ.
+	* doc/html/*: Regenerate.
+
 2020-05-01  Jonathan Wakely  <jwakely@redhat.com>
 
 	Backport from mainline

libstdc++-v3/doc/html/faq.html

@@ -813,7 +813,7 @@
     and <a class="link" href="manual/backwards.html" title="Backwards Compatibility">backwards
     compatibility</a> documentation.
     </p><p>
-    The <a class="link" href="https://web.archive.org/web/20171225062613/http://www.sgi.com/tech/stl/FAQ.html" target="_top">FAQ</a>
+    The <a class="link" href="https://web.archive.org/web/20171104092813/http://www.sgi.com/tech/stl/FAQ.html" target="_top">FAQ</a>
     for SGI's STL is still recommended reading.
     </p></td></tr><tr class="question"><td align="left" valign="top"><a id="faq.extensions_and_backwards_compat"></a><a id="q-extensions_and_backwards_compat"></a><p><strong>7.4.</strong></p></td><td align="left" valign="top"><p>
       Extensions and Backward Compatibility

libstdc++-v3/doc/xml/faq.xml

@@ -1150,7 +1150,7 @@
     compatibility</link> documentation.
     </para>
     <para>
-    The <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://web.archive.org/web/20171225062613/http://www.sgi.com/tech/stl/FAQ.html">FAQ</link>
+    The <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://web.archive.org/web/20171104092813/http://www.sgi.com/tech/stl/FAQ.html">FAQ</link>
     for SGI's STL is still recommended reading.
     </para>
   </answer>