MSG_task_execute(). This value has to be >=0.
* \param message_size a value of the amount of data (in bytes) needed to
transfer this new task. If 0, then it cannot be transfered with
MSG_task_execute(). This value has to be >=0.
* \param message_size a value of the amount of data (in bytes) needed to
transfer this new task. If 0, then it cannot be transfered with