INT 2F U - DRIVER.SYS support - INSTALLATION CHECK                              
	AX = 0800h
Return: AL = status
	    00h not installed, OK to install
	    01h not installed, not OK to install
	    FFh installed
Desc:	determine whether the internal support code used by DRIVER.SYS is
	  present; it is always present in DOS 3.2+
Note:	supported by DR DOS 5.0 and Novell DOS 7