|R0||Task handle returned by Wimp_Initialise|
The purpose of this call is to inform the Wimp that a task is about to terminate.
This must be called immediately before the task terminates by calling OS_Exit. If it is not, then the task has a last chance to trap its shutdown by means of the Service_WimpCloseDown (which will also be called if the task exits normally).
The task handle and magic word are only required if closing a task which is not presently paged in. e.g a module.