/* call-seq: * krb5.get_init_creds_keytab(principal = nil, keytab = nil, service = nil, ccache = nil) * * Acquire credentials for +principal+ from +keytab+ using +service+. If * no principal is specified, then a principal is derived from the service * name. If no service name is specified, kerberos defaults to "host". * * If no keytab file is provided, the default keytab file is used. This is * typically /etc/krb5.keytab. * * If +ccache+ is supplied and is a Kerberos::Krb5::CredentialsCache, the * resulting credentials will be stored in the credential cache. */ static VALUE rkrb5_get_init_creds_keytab(int argc, VALUE* argv, VALUE self){