Switch commoncpp2 to ucommon to solve dependency conflicts.

libccrtp was depending on commoncpp2, and have been replaced by a version
depending on ucommon as well.
diff --git a/jni/libzrtp/sources/zrtp/libzrtpcpp/ZrtpUserCallback.h b/jni/libzrtp/sources/zrtp/libzrtpcpp/ZrtpUserCallback.h
index d3c9f9d..3e4871c 100644
--- a/jni/libzrtp/sources/zrtp/libzrtpcpp/ZrtpUserCallback.h
+++ b/jni/libzrtp/sources/zrtp/libzrtpcpp/ZrtpUserCallback.h
@@ -1,8 +1,8 @@
 /*

-  Copyright (C) 2006-2013 Werner Dittmann

+  Copyright (C) 2006-2008 Werner Dittmann

 

   This program is free software: you can redistribute it and/or modify

-  it under the terms of the GNU Lesser General Public License as published by

+  it under the terms of the GNU General Public License as published by

   the Free Software Foundation, either version 3 of the License, or

   (at your option) any later version.