INT 15 - TopView - "SETBIT" - SCHEDULE ONE OR MORE 2ND-LEVEL INTERRUPTS
        AX = 1015h
        BX = bit mask for interrupts to post
Return: indicated routines will be called: (DV 2.0x) at next task switch
                                           (DV 2.2x) immediately
SeeAlso: AX=1014h
Notes:  this is one of the few TopView calls which are allowed from a hardware
          interrupt handler
        the handler will be called with ES containing the segment of the handle
          of the next task to be executed; on return, ES must be the segment of
          a task handle