Expect: AX    0006H
BX    ID of the session
ES:DI addr of switcher's service-entry address
Return: AX    0000H (you must return 0 in all cases)
Info: Task switchers call this to let you know that a session is about
to be destroyed.  It gives you a chance perform any cleanup
needed to process the end of a session.

When called, interrupts are enabled you may use all DOS fns.

BX will contain the session ID of the session that is about to be
destroyed. (Note: it need not be the current active session).

ES:SI will contain the task switcher's service entry address.  Use this
address if you need to call any task-switcher service fns.

Return: AX=0000H you must return 0.  Tasks have not veto power here.

Notes: You may get this call without first seeing a SwNtfyFn 0006H
(session is being created).  That call is broadcasted when some
task has vetoed the new session.  In that case, you may ignore
this call.

INT 2fH 4bxxH (switcher functions)
- -

SwNtfy Fn 0006H: Switcher Is Destroying a Session