* agent/agent.h (agent_kem_decrypt): Remove OPTION argument.
* agent/command.c (cmd_pkdecrypt): No option is needed.
* agent/pkdecrypt.c (composite_pgp_kem_decrypt): Use
gnupg_ecc_kem_simple_kdf.
(ecc_kem_decrypt): Support the S/MIME case too.  Follow the change of
gnupg_ecc_kem_kdf.
(agent_kem_decrypt): Remove OPTION argument.  Also support the S/MIME
case.
* common/kem.c (gnupg_ecc_kem_kdf): Support the S/MIME case too.
Don't support simple ECC part for combined KEM.
(gnupg_ecc_kem_simple_kdf): New.
* common/util.h (gnupg_ecc_kem_kdf): Support the S/MIME case too.
(gnupg_ecc_kem_simple_kdf): New.
* g10/pkglue.c (do_encrypt_kem): Use gnupg_ecc_kem_simple_kdf.
Use gnupg_ecc_kem_kdf with IS_GPG=1.