Develop

The documentation is wrong regarding what happens when the "known hosts" and "private key" options are NULL. According to the documentation at http://api.libssh.org/stable/group__libssh__session.html#ga7a801b85800baa3f4e16f5b47db0a73d they both default to the system default, which is not always ~/.ssh/*.

P.S.: I don't know why GitHub keeps telling me that I would like to pull request more than one commit when it is actually only one. I pulled from upstream (rtrlib/rtrlib), pushed to origin (my fork), made my changes, pushed to origin and filed the pull request.