extending bandwidth tracker api to support notifications


git-svn-id: https://gnunet.org/svn/gnunet@32116 140774ce-b5e7-0310-ab8b-a85725594a96
-doxygen

git-svn-id: https://gnunet.org/svn/gnunet@32117 140774ce-b5e7-0310-ab8b-a85725594a96
Skip testcase when DNS is not available

* gns/test_gns_cname_lookup.sh: Check if DNS resolution works and skip test if
it doesn't work.


git-svn-id: https://gnunet.org/svn/gnunet@32118 140774ce-b5e7-0310-ab8b-a85725594a96