INT 2F - NETWORK - INSTALLATION CHECK
AX = B800h
Return: AL = status
00h not 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 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.