Int 15 Fn 530A  - Advanced Power Management Specification - Get Power Sta  [p]

   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