INT 10,1A - Video Display Combination (VGA)

	AH = 1A
	AL = 00 get video display combination
	   = 01 set video display combination
	     BL = active display  (see table below)
	     BH = inactive display

	on return:
	AL = 1A, if a valid function was requested in AH
	BL = active display  (AL=00, see table below)
	BH = inactive display  (AL=00)

	Valid display codes:

	 FF  Unrecognized video system
	 00  No display
	 01  MDA with monochrome display
	 02  CGA with color display
	 03  Reserved
	 04  EGA with color display
	 05  EGA with monochrome display
	 06  Professional graphics controller
	 07  VGA with analog monochrome display
	 08  VGA with analog color display
	 09  Reserved
	 0A  MCGA with digital color display
	 0B  MCGA with analog monochrome display
	 0C  MCGA with analog color display

	- returns value at byte 40:8A indicating display combination status
	- used to detect video display capabilities