Allow to create javadocs for multiple packages

Change-Id: Ia3de0458603dbe14f510b2edadf6ea44406b820e
diff --git a/tools/java_doc.defs b/tools/java_doc.defs
index d117bda..514a730 100644
--- a/tools/java_doc.defs
+++ b/tools/java_doc.defs
@@ -1,7 +1,7 @@
 def java_doc(
     name,
     title,
-    pkg,
+    pkgs,
     paths,
     srcs = [],
     deps = [],
@@ -24,7 +24,8 @@
       '-notimestamp',
       '-windowtitle "' + title + '"',
       '-link http://docs.oracle.com/javase/7/docs/api',
-      '-subpackages ' + pkg,
+      '-subpackages ',
+      ':'.join(pkgs),
       '-sourcepath ',
       ':'.join(sourcepath),
       ' -classpath ',