Add new libraries to root/index.html

index.html

@@ -55,7 +55,8 @@
 
   <h3>Changes in this release</h3>
 
-  <p>This release includes ?? new libraries (..),
+  <p>This release includes 1 new library
+  (<a href="libs/coroutine2/">Coroutine2</a>),
   as well as updates to many existing libraries. See
   <a href="http://www.boost.org/users/history/version_1_59_0.html">Release
   History</a> for more information.</p>