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libccrtp was depending on commoncpp2, and have been replaced by a version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/libccrtp/sources/src/socket.cpp b/jni/libccrtp/sources/src/socket.cpp
index 0377dd8..5a5189f 100644
--- a/jni/libccrtp/sources/src/socket.cpp
+++ b/jni/libccrtp/sources/src/socket.cpp
@@ -41,13 +41,9 @@
 #include "private.h"
 #include <ccrtp/channel.h>
 
-#ifdef  CCXX_NAMESPACES
-namespace ost {
-#endif
+NAMESPACE_COMMONCPP
 
-#ifdef  CCXX_NAMESPACES
-}
-#endif
+END_NAMESPACE
 
 /** EMACS **
  * Local variables: