/*
 *  call-seq:
 *     query.add(span_query) -> self
 *     query << span_query -> self
 *
 *  Add a clause to the SpanOrQuery. Note that clauses must be SpanQueries,
 *  not other types of query.
 */
static VALUE
frt_spanoq_add(VALUE self, VALUE rclause)
{
    GET_Q();
    Query *clause;
    Data_Get_Struct(rclause, Query, clause);
    spanoq_add_clause(q, clause);
    return self;
}