`elliptic_curve::SecretKey` supports `to_sec1_der_with_oid`

[heliannuuthus]

I see that the to_sec1_der() method currently specifies EcParameters::NamedCurve as Option::None. In the protocol(sec1#114), I see that this field is optional. Can I set it to the correct value or provide another method to return OID?