ssh/server-type.c: Improve printing of server objects

* ssh/server-type.h (server_data): Add `options' field.
* ssh/server-type.c (mark_server): Mark `options' field.
  (guile_ssh_make_server): Initialize `options' field.
  (print_server): New procedure.
  (init_server_type): Register server printer procedure.
* ssh/server-func.c (guile_ssh_server_set_x): Add an option to the
  server optons.
* ssh/server-func.h (server_options): Export.
* NEWS: Update.