(opts): Add -f option.
(restore_flags): New variable.
(usage): Clarify working of save action. Add restore action. Add
description for -f/--force option.
(set_privilege): Drop function. The Cygwin DLL is doing that anyway.
(cmd_save): Drop call to set_privilege.
(cmd_restore): New function.
(main): Handle -f/--force option.