Upgrade copyright

snicoll · snicoll · commit c38381a54ddd · 2016-07-04T12:48:08.000+02:00
diff --git a/src/reference/docbook/index.xml b/src/reference/docbook/index.xml
@@ -160,7 +160,7 @@
     </authorgroup>
 
     <copyright>
-      <year>2004-2013</year>
+      <year>2004-2016</year>
     </copyright>
 
     <legalnotice>
