Expect: AX    0007H
BX    flags: 0001H this is the only task switcher
0000H other task switchers exist
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 when they are
terminating.  It gives you a chance perform any necessary cleanup
and disable any extra processing that you were doing to coexist
with the switcher.

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

BX bit 0 will be set (BX=0001H) is this is the only active task
switcher.  All other bits will be 0.

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.

INT 2fH 4bxxH (switcher functions)
- -

SwNtfy Fn 0007H: Switcher Is Exiting