Revision 33640

   Fix a few issues affecting the usage of tree friends in PROOF (see reports on the forum)
   - In TDSet:
      - Add friend alias as an option to the URL ("friend_alias=<alias>|") instead of an
        object string in a TPair (non streamable!)
   - In TVirtualPacketizer::CreateNewPacket
      - Adapt to the change in TDSet
   - In TEventIter:
      - Adapt to the change in TDSet
      - Make sure that the file with the friend is closed only when is not used anymore.

   The patch also fixes an issue with the locality check for files in TDSet.