Unlock

        Entry:
          AH = 13h
          AL = drive number or 00h
          ES:SI = Ethernet address or 0000h:0000h
          DS:BX -> 31-byte ASCIZ semaphore name
        Return:
          AL = status (see also AH=11h)
            1 semaphore not logged
INT 61 - reserved for user interrupt
INT 62 - reserved for user interrupt
INT 63 - reserved for user interrupt

        Note:   Some floppy controller BIOSes seem to hook INT 40 and
                place the old value here (more details to come, I hope)