krb5int_dns_init
ret = krb5int_dns_init(&ds, txtname, C_IN, T_TXT);
int krb5int_dns_init(struct krb5int_dns_state **, char *, int, int);
size = krb5int_dns_init(&ds, name, C_IN, T_URI);
size = krb5int_dns_init(&ds, name, C_IN, T_SRV);