* gnu/packages/ssh.scm (libssh): Update to 0.9.0. Of particular
interest for robust offloading is libssh commit
e4e51ccc1340e313c203842d0180a1c4e33c95cc, which fixes a bug whereby,
instead of honoring the per-session timeout, 'ssh_channel_read_timeout'
would end up passing an infinite timeout to 'poll':
see <https://bugs.libssh.org/T33>