public Object
sendAsync(final Message query, final ResolverListener listener) {
	Resolution res = new Resolution(this, query);
	res.startAsync(listener);
	return res;
}
Asynchronously sends a message to multiple servers, potentially multiple
times, registering a listener to receive a callback on success or exception.
Multiple asynchronous lookups can be performed in parallel.  Since the
callback may be invoked before the function returns, external
synchronization is necessary.
@param query The query to send
@param listener The object containing the callbacks.
@return An identifier, which is also a parameter in the callback
src/main/java/core/org/xbill/DNS/ExtendedResolver.java