Fix ref links.

libs/libraries.htm

@@ -290,7 +290,7 @@ how to download, build, and install the libraries.</p>
     <li><a href="rational/index.html">rational</a> - A rational
         number class, from Paul Moore.</li>
 
-    <li><a href="bind/ref.html">ref</a> - A utility library for
+    <li><a href="core/ref.html">ref</a> - A utility library for
     passing references to generic functions, from Jaako J&auml;rvi,
     Peter Dimov, Doug Gregor, and Dave Abrahams.</li>
 
@@ -575,7 +575,7 @@ how to download, build, and install the libraries.</p>
     <li><a href="phoenix/index.html">Phoenix</a> - Define small unnamed
     function objects at the actual call site, and more, from Joel de Guzman, Dan
     Marsden and Thomas Heller</li>
-    <li><a href="bind/ref.html">ref</a> - A utility library for
+    <li><a href="core/ref.html">ref</a> - A utility library for
     passing references to generic functions, from Jaako J&auml;rvi,
     Peter Dimov, Doug Gregor, and Dave Abrahams.</li>