INT 21 - DOS 1+ - SET VERIFY FLAG                                               
	AH = 2Eh
	DL = 00h (DOS 1.x/2.x only)
	AL = new state of verify flag
	    00h off
	    01h on
Notes:	default state at system boot is OFF
	when ON, all disk writes are verified provided the device driver
	  supports read-after-write verification
SeeAlso: AH=54h