title: json-c json_object_to_json_string() equivalent api in jansson library
body: <p>In the Current code i'm using json-c. i'm migrating to jansson.
  need an equivalent api in jansson which converts the json_object_to_json_string. 
  i found one but it needs a json string object otherwise it is returning null.</p>
  
  <p>const char *json_string_value(const json_t *string)  - not working </p>
  
  <p>but my input is a <code>JSON</code> object not a <code>JSON</code> string </p>
  
  <h2>sample:</h2>
  
  <pre><code>json_object *jobj = json_object_new_object();
  
  ....
  
  const char *final_string = json_object_to_json_string(jobj);
  </code></pre>
  
  <p>Thanks.</p>