THRIFT-833. java: build.xml in lib/java is missing a classpathref attribute for the javadoc task

Turns out there was a missing classpathref that was causing lots of spurious warnings to be printed. This patch fixes that.

Patch: Nate McCall

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@980548 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/java/build.xml b/lib/java/build.xml
index 57be5e3..b68c95a 100644
--- a/lib/java/build.xml
+++ b/lib/java/build.xml
@@ -129,7 +129,8 @@
       destdir="${javadoc}"
       version="true"
       windowtitle="Thrift Java API"
-      doctitle="Thrift Java API">
+      doctitle="Thrift Java API"
+      classpathref="test.classpath">
     </javadoc>
   </target>