ecc: Add backward compatibility support for Ed25519 key in SEXP.
* cipher/ecc-curves.c (_gcry_ecc_get_curve): Support Ed25519 keys with
parameter {p,a,b,g,n}.- Fixes-commit: 6f8b1d4cb798375e6d830fd6b73c71da93ee5f3f
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>