INT 2F - NETWORK - INSTALLATION CHECK                                           
	AX = B800h
Return: AL = status
	    00h	    not installed
	    nonzero installed
	      BX = installed component flags (test in this order!)
		   bit 6   server
		   bit 2   messenger
		   bit 7   receiver
		   bit 3   redirector
		   bit 1   LANPUP (LANtastic 4.0)
Notes:	this function is supported by PCIBM PC LAN Program, LAN Manager, LANtastic,
	  NetWare Lite, SilverNET, 10NET, etc.
	LANtastic and NetWare Lite use only BL for the return value, preserving
	  BH; LAN Manager and DOS LAN Requester return BH=00h.	This permits
	  differentiation between those two groups by setting BH to a nonzero
	  value before the call and checking its value on return.
SeeAlso: AX=4E53h,AX=B809h