Encoding:
    SILC_ASN1_SET
    SILC_ASN1_SET_T(opts, tag)

    Decoding:
    SILC_ASN1_SET
    SILC_ASN1_SET_T(opts, tag)

    Macro used to encode or decode set.  The set must be terminated
    with SILC_ASN1_END.

    The `opts' is SilcAsn1Options.  The `tag' is a tag number.

    silc_asn1_encode(asn1, tree,
                     SILC_ASN1_SET_T(SILC_ASN1_EXPLICIT, 0),
                       SILC_ASN1_BOOLEAN(boolval),
                     SILC_ASN1_END, SILC_ASN1_END);