+ check_ssh using libssh now to verify host fingerprint, and openssh version

if libssh is not found, the fingerprint / openssh-version-detection functions are not compiled in.
for backward compatibility the parameters of original check_ssh stay untouched
for checking the fingerprint && || the openssh version use -f and or -o

Signed-off-by: hjanuschka <helmut@januschka.com>