INT 2F - PCIBM PC LAN PROGRAM REDIRIFS.EXE internal - INSTALLATION CHECK
	AX = BF00h
Return: AL = FFh if installed
Note:	this function is also supported by NetSoft's DOS-NET v1.20+; however,
	  none of the remaining BFxxh calls are supported
SeeAlso: AX=BF01h,AX=BF80h,INT 2A/AX=4147h