handle subtyping better.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@11392 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/tasks/Ant.java

@@ -268,7 +268,7 @@ public class Ant extends Builder {
         }
 
         public Ant newInstance(StaplerRequest req, JSONObject formData) throws FormException {
-            return req.bindJSON(Ant.class,formData);
+            return (Ant)req.bindJSON(clazz,formData);
         }
 
     //