fixes for doxygen


git-svn-id: https://gnunet.org/svn/gnunet@32040 140774ce-b5e7-0310-ab8b-a85725594a96
solving slow shutdown issue: statistic was not destroyed


git-svn-id: https://gnunet.org/svn/gnunet@32041 140774ce-b5e7-0310-ab8b-a85725594a96