add TUdpSocket as friend.

git-svn-id: http://root.cern.ch/svn/root/trunk@41632 27541ba8-7e3a-0410-8455-c3a389f83636

net/net/inc/TMessage.h

@@ -39,6 +39,7 @@ class TMessage : public TBufferFile {
 
 friend class TAuthenticate;
 friend class TSocket;
+friend class TUdpSocket;
 friend class TPSocket;
 friend class TXSocket;