This method tells an object to forward the message in the form of an
OM_UPDATE message to all the objects in its broadcast list.  The
modelclass does not map the attributes in these OM_UPDATE messages.
Because modelclass inherits behavior from icclass, if the model has an
ICA_TARGET and ICA_MAP, it will also send a mapped OM_UPDATE message to
its ICA_TARGET.  The return values for these methods are not explicitly
defined.  See the rootclass OM_NOTIFY/OM_UPDATE and icclass
OM_NOTIFY/OM_UPDATE descriptions for more information.