void recycle(final InputStream newIn) {
        count = 0;
        pos = 0;
        streamPosition = 0;
        in = newIn;
        markpos = -1;
        marklimit = 0;
    }
Point at a new input stream and reset our markers. Used to avoid
allocating new buffers.

@param newIn new stream to read
stroom-data/stroom-data-store-impl-fs/src/main/java/stroom/data/store/impl/fs/BlockBufferedInputStream.java