INT 15 - Advanced Power Management Specification - GET POWER STATUS
        AX = 530Ah
        BX = 0001h
Return: CF clear if successful
            BH = AC line status
                00h off-line
                01h on-line
                FFh unknown
                other reserved
            BL = battery status
                00h high
                01h low
                02h critical
                03h charging
                FFh unknown
                other reserved
            CL = remaining battery life
                00h-64h (0-100) percentage of full charge
                FFh unknown
        CF set on error
            AH = error code (09h) (see AX=5300h)
Note:   should not be called from within a hardware interrupt handler to avoid
          reentrance problems