@Override
    public void addSegment() throws IOException {
        addSegment(this.position);
    }
Adds a segment boundary to the output stream. All bytes written between
the start of the output or the last boundary will be considered a segment
by the <code>RASegmentInputStream</code>.
stroom-data/stroom-data-store-impl-fs/src/main/java/stroom/data/store/impl/fs/RASegmentOutputStream.java