title: JSON_BIGINT_AS_STRING backporting
body: <p>From my understanding, <code>JSON_BIGINT_AS_STRING</code> is 5.4+ only. I need the reproduce the same behavior in 5.1+ environments. The code is meant to be distributed and I have no control over environments it will run on.  What are my options (apart from writing my own json parser)? Is there any established and well-tested solution? </p>