INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (PSIBM PS/2, any model, VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) - VIDEO REFRESH CONTROL
	AH = 12h
	BL = 36h
	AL = new state
	    00h enable refresh
	    01h disable refresh
Return: AL = 12h if function supported
Desc:	specify whether the contents of video memory should be displayed on
	  the screen; disabling refresh effectively blanks the screen
Note:	when display refresh is disabled, the entire screen displays the color
	  specified by the DAC(Digital-to-Analog Converter) A hardware device (in its simplest form, nothing more than a set of interconnected resistors) which converts a digital number into an analog signal whose voltage is proportional to the value of the digital number.  VGAVideo Graphics Array and later color video boards use DACs to convert color values into the analog signals sent to the display; sound boards normally use DACs as well. color register 00h; thus to actually blank the
	  screen, the application must first ensure that that register has been
	  set to black
BUG:	GEM/VIEWMAX ET3000 and ET4000 drivers dated 1988/6/23 do not correctly
	  reenable refresh after the screen has been blanked due to inactivity,
	  resulting in a total loss of video synchronization
SeeAlso: AX=BF05h