Add new attribute "sourcefilename" to "class" element in XML report (#702)

This allows to unambiguously relate classes to source files in case of
multiple top level classes.
diff --git a/org.jacoco.doc/docroot/doc/changes.html b/org.jacoco.doc/docroot/doc/changes.html
index 5299b4e..bed7d9d 100644
--- a/org.jacoco.doc/docroot/doc/changes.html
+++ b/org.jacoco.doc/docroot/doc/changes.html
@@ -45,6 +45,14 @@
       (GitHub <a href="https://github.com/jacoco/jacoco/issues/703">#703</a>).</li>
 </ul>
 
+<h3>API Changes</h3>
+<ul>
+  <li>The XML report now has an optional attribute <code>sourcefilename</code>
+      on the <code>class</code> element to allow unambiguously relate classes
+      to source files. The JaCoCo DTD version has been updated to 1.1
+      (GitHub <a href="https://github.com/jacoco/jacoco/issues/702">#702</a>).</li>
+</ul>
+
 <h2>Release 0.8.1 (2018/03/21)</h2>
 
 <h3>New Features</h3>