INT 2F U - DOS 3.3+ DISPLAY.SYS internal - INSTALLATION CHECK                   
	AX = AD00h
Return: AL = FFh if installed
	    BX = ??? (0100h for MS-DOS 3.3+)
Note:	DOS 5+ DISPLAY.SYS chains to previous handler if AL is not one of the
	  subfunctions listed here
SeeAlso: AX=AD01h"DISPLAY",AX=AD02h"DISPLAY"