ssh/*.c: Improve the docstrings format

* ssh/auth.c, ssh/channel-func.c, ssh/channel-type.c, ssh/key-func.c,
  ssh/key-type.c, ssh/log.c, ssh/message-func.c, ssh/message-type.c,
  ssh/server-func.c, ssh/session-type.c, ssh/version.c: Improve the
  docstrings format.