INT 15 - Rational Systems DOS/4GW - ???                                         
	AX = BF04h
	BX = PSPsee Program Segment Prefix segment of extender
Return: nothing???
Notes:	if BX is not the PSPsee Program Segment Prefix segment of the extender, it passes the call down
	  the INT 15 chain; this allows nested instances of the extender
	grabs INT 2Fh and installs handlers for INT 2F/AX=1605h-1607h
SeeAlso: INT 2F/AX=1607h/BX=22C0h