agent: For ECC, use opaque MPI for key representation.
* agent/cvt-openpgp.c (scan_pgp_format): New with SOS support. (do_unprotect): Use scan_pgp_format, handle opaque MPI for ECC. (convert_from_openpgp_main): Use opaque MPI for ECC. (apply_protection): Set GCRYMPI_FLAG_USER1 flag for encrypted secret. (extract_private_key): Use "/qd" for ECC, opaque MPI.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>