* agent/agent.h (agent_card_pkdecrypt): Fix the type of R_BUF.
* agent/call-scd.c (agent_card_pkdecrypt): Likewise.
* agent/divert-scd.c (divert_pkdecrypt): Follow the change.
* agent/divert-scd.c (agent_card_ecc_kem): The prefix may be
0x02 or 0x03 depending on hidden y-coordinate.