users building ant should place required external jars under lib/optional

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@356985 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/install.html

@@ -253,8 +253,8 @@ kjc.</b>
 
 <p>Make sure you have downloaded any auxiliary jars required to
 build tasks you are interested in. These should either be available
-on the CLASSPATH or added to the <code>lib</code>
-directory.
+on the CLASSPATH or added to the <code>lib/optional</code>
+directory of the source tree.
 See <a href="#librarydependencies">Library Dependencies</a>
 for a list of jar requirements for various features.
 Note that this will make the auxiliary jars