INT 10 - VIDEO - Compaq Portable/Systempro Extensions - GET ENVIRONMENT
        AX = BF03h
        BX = 0000h
Return: BH = active monitor
            00h = external
            01h = internal
        BL = master mode
            00h = switchable VDU not present
            04h = CGA
            05h = EGA
            07h = MDA
            08h = switchable LCD controller present
        CH = 00h (reserved)
        CL = switchable VDU mode supported
            bit  0   = CGA supported
            bits 1,2 = reserved (1)
            bit  3   = MDA supported
            bits 4-7 = reserved (1)
        DH = internal monitor type
            00h = none
            01h = Dual-mode monitor
            02h = 5153 RGB monitor
            03h = Compaq Color monitor
            04h = 640x400 flat panel
            07h = LCD VGA
        DL = external monitor type
            00h = none
            01h = dual-mode monitor
            02h = 5153 RGB monitor
            03h = Compaq Color monitor
            04h = 640x400 flat panel
            05h = VGC monochrome
            06h = VGC color
SeeAlso: AX=BF00h,AX=BF01h,AX=BF02h