agent: pksign result conversion to sexp to upper layer.
* agent/agent.h (divert_pksign): Add R_SIGLEN argument. * agent/divert-scd.c (divert_pksign): Return length at R_SIGLEN. * agent/call-scd.c (agent_card_pksign): Move composition of S-expression to... * agent/pksign.c (agent_pksign_do): ... here.
Composing S-expression would be better to be done by SCDaemon.