move proxy and annotation code from C++ to Java

This allows code shrinkers to remove it if it's not used by the application.

classpath/avian/ClassAddendum.java

@@ -0,0 +1,15 @@
+/* Copyright (c) 2009, Avian Contributors
+
+   Permission to use, copy, modify, and/or distribute this software
+   for any purpose with or without fee is hereby granted, provided
+   that the above copyright notice and this permission notice appear
+   in all copies.
+
+   There is NO WARRANTY for this software.  See license.txt for
+   details. */
+
+package avian;
+
+public class ClassAddendum extends Addendum {
+  public Object[] signers;
+}