void resolveReferences()
    {
        extendedMessage = getProto().findMessageReference(getExtendedMessageFullName(),
                getEnclosingNamespace());
        if (extendedMessage == null)
        {
            throw err("The message " + getExtendedMessageFullName()
                    + " is not defined", getProto());
        }
        extendedMessage.extend(this);

        if (!standardOptions.isEmpty())
            proto.references.add(new ConfiguredReference(standardOptions, extraOptions, getExtendedMessageFullName()));
    }
Represents an extend block declared in either the {@link Proto} or nested in a {@link Message}.

@author Philippe Laflamme
protostuff-parser/src/main/java/io/protostuff/parser/Extension.java