cleaning up scalar product client API

git-svn-id: https://gnunet.org/svn/gnunet@33376 140774ce-b5e7-0310-ab8b-a85725594a96
-a bit more towards following coding conventions

git-svn-id: https://gnunet.org/svn/gnunet@33377 140774ce-b5e7-0310-ab8b-a85725594a96