new underlay API


git-svn-id: https://gnunet.org/svn/gnunet@31236 140774ce-b5e7-0310-ab8b-a85725594a96
- doxygen


git-svn-id: https://gnunet.org/svn/gnunet@31237 140774ce-b5e7-0310-ab8b-a85725594a96
- fix handle for tunnel queueing during KX


git-svn-id: https://gnunet.org/svn/gnunet@31238 140774ce-b5e7-0310-ab8b-a85725594a96