add javadoc link to JDK 5 apis

git-svn-id: https://google-guice.googlecode.com/svn/trunk@125 d779f126-a31b-0410-b53b-1d3aecad763e
diff --git a/build.xml b/build.xml
index 43c5e06..d295206 100644
--- a/build.xml
+++ b/build.xml
@@ -118,6 +118,7 @@
       </sourcepath>
       <classpath refid="compile.classpath"/>
       <link href="http://aopalliance.sourceforge.net/doc"/>
+      <link href="http://java.sun.com/javase/6/docs/api"/>
     </javadoc>
   </target>