Expects: AX    0002H
ES:DI address of new service function handler
Returns: CF    Carry Flag is clear (NC) is successful and...
AX    result code: 0000H = suspended
0001H = not suspended, don't start
0002H = not suspended, OK to start
Info: This service is used ONLY by a task-switching program that wants
to suspend the active task switcher and provide task-switching

Applications should not use this service.  If you need to keep a
switcher from suspending a session, you must hook into the
notification chain (via SwNtfyFn 0004H) and handle SwNtfyFn 0001H
(query suspend) calls.

INT 2fH 4bxxH (switcher functions)
- -

SwSrvc Fn 0002H: Suspend Switcher