INT 10 - VIDEO - Compaq 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 (see below)
        DL = external monitor type (see below)
SeeAlso: AH=1Ah,AX=BF00h,AX=BF01h,AX=BF02h

Values for 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
 07h    LCD VGA

.