- fix segfault at get size of null hello

git-svn-id: https://gnunet.org/svn/gnunet@32211 140774ce-b5e7-0310-ab8b-a85725594a96
fixing compile warning: cast to types required in doxygen documentation


git-svn-id: https://gnunet.org/svn/gnunet@32212 140774ce-b5e7-0310-ab8b-a85725594a96
- add hello lib

git-svn-id: https://gnunet.org/svn/gnunet@32213 140774ce-b5e7-0310-ab8b-a85725594a96