INT 21 - DOS 1+ - GET CURRENT DEFAULT DRIVE

	AH = 19h
Return: AL = drive (00h = A:, 01h = B:, etc)
Note:	Novell NetWare uses the fact that DOS 2.x COMMAND.COM issues this call
	  from a particular location every time it starts a command to
	  determine when to issue an automatic EOJ
SeeAlso: AH=0Eh,AH=47h,AH=BBh