Fix a broken link.

[SVN r36647]

index.htm

@@ -463,7 +463,7 @@
                           </li>
 
                       <li><span class="library"><a href=
-                      "../doc/html/signals.html">Signals Library</a>:</span>
+                      "doc/html/signals.html">Signals Library</a>:</span>
                       More improvements to signal invocation performance from
                       Robert Zeh.</li>