Macro asn1_cereal::ber_choice

macro_rules! ber_choice {
    ($rs_type:ident, [$($opts:tt)*], $asn1_type:expr, $($args:tt)*) => { ... };
    ($rs_type:ident, $asn1_type:expr, $($args:tt)*) => { ... };
}

Generate the Asn1Info implemention for an ASN.1 Choice type, represented by a Rust enum.