@Override
    public void writeString(int fieldNumber, CharSequence value, boolean repeated) throws IOException
    {
        // TODO the original implementation is a lot more complex, is this compatible?
        byte[] strbytes = value.toString().getBytes("UTF-8");
        writeByteArray(fieldNumber, strbytes, repeated);
    }
Output that differs from the standard by attempting to avoid extra copies of large ByteBuffer fields. When used with
ByteBuffer=true compiler option, we can splice in ByteBuffer objects without copying them. Most of the magic lives in
LinkBuffer, so this class exists just to serialize to a LinkBuffer.

@author Ryan Rawson
protostuff-core/src/main/java/io/protostuff/LowCopyProtobufOutput.java