scd: Add DES authentication for PIV card.
* scd/app-piv.c (flush_cached_data): New. (auth_adm_key): New. (set_adm_key): New. (do_setattr): New. * scd/command.c (MAXLEN_SETATTRDATA): New. (cmd_setattr): Add an inquire option.
- Signed-off-by: Werner Koch <wk@gnupg.org>