SwNtfy Fn 0005H: Switcher Is Creating a Session

  Expect: AX    0005H
          BX    ID for the new session
          ES:DI addr of switcher's service-entry address
  Return: AX    0000H if OK to create the session
                0001H if you object to the new session
    Info: Task switchers call this to let you know that a new session is
          about to be created.  It gives you a chance to object to the new
          session (fir instance, if you don't have enough memory to track
          it safely).

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

       BX will contain the session ID of the new session.  The high 4 bits
          are the Switcher ID (see INT 2fH 4b03H) and the low 12 bits are
          an arbitrary (not necessarily sequential) number.

    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 to indicate that you don't object to the new session. If
          any task returns 0001H, the session will not be started and all
          tasks may receive SwNtfyFn 0006H (session has been destroyed).

See Also: Switcher Services and Notifications
          INT 2fH 4bxxH (switcher functions)