add a link to zipfileset in the section about types supporting references

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@274520 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/using.html

@@ -530,7 +530,8 @@ example.</p>
 &lt;/project&gt;
 </pre></blockquote>
 <p>All tasks that use nested elements for <a
-href="CoreTypes/patternset.html">PatternSet</a>s, <a href="CoreTypes/fileset.html">FileSet</a>s or
+href="CoreTypes/patternset.html">PatternSet</a>s, <a href="CoreTypes/fileset.html">FileSet</a>s,
+<a href="CoreTypes/zipfileset.html">ZipFileSet</a>s  or
 <a href="#path">path-like structures</a> accept references to these
 structures as well.</p>