* Stores 'req' on heap for asynchrnous use.
* Returns a handler to the stored 'req' or NULL on memory depletion.
* The count of reference to 'req' is incremented on success
* (see afb_req_addref).
*/
* Stores 'req' on heap for asynchrnous use.
* Returns a handler to the stored 'req' or NULL on memory depletion.
* The count of reference to 'req' is incremented on success
* (see afb_req_addref).
*/