* src/keyinfo.c (_ksba_keyinfo_from_sexp): Skip writing curve
parameter in algoinfo mode.
(PKALGO_NONE): New.
(curve_names): Add field pkalgo and set for rfc8410 algos.
(get_ecc_curve_oid): New arg r_pkalgo.
(_ksba_keyinfo_from_sexp): Take are of a forced algo.  Add code path
for rfc8410 public key.
* src/certreq.h (struct ksba_certreq_s): Add flag 'is_ecc'.
* src/certreq.c (ksba_certreq_add_extension): Set that flag.
(ksba_certreq_set_sig_val): Use sig_val.is_ecc also for EdDSA.
(build_cri): Rewrite using the DER builder.