* g10/call-agent.h (agent_card_info_s): Rename the "*valid" fields to
"*len".
* g10/call-agent.c (unhexify_fpr): Change to take a FPRLEN and to
return the actual length.
(agent_release_card_info): Adjust for these changes.
* g10/card-util.c (print_sha1_fpr): Rename to print_shax_fpr and add
arg FPRLEN.  Change all callers to pass the length.
(print_sha1_fpr_colon): Rename to print_shax_fpr_colon and add arg
FPRLEN.  Change all callers to pass the length.
(fpr_is_zero): Add arg FPRLEN.
(fpr_is_ff): Ditto.
(show_card_key_info): Use the new functions.
* g10/skclist.c (enum_secret_keys): Use MAX_FINGERPRINT_LEN.