INT 2A - NETWORK - CHECK DIRECT I/O                                             
	AX = 0300h
	DS:SI -> ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. device name (may be full path or only drive specifier--
		  must include the colon)
Return: CF clear if direct physical addressing (INT 13,INT 25) permissible
	CF set if access via files only
Notes:	do not use direct disk accesses if this function returns CF set or the
	  device is redirected (INT 21/AX=5F02h)
	use AH=00h to determine whether the network is installed; if not,
	  direct physical access is allowed
	may take some time to execute, so programs which need to check
	  frequently should save the result of the first call
	this function is called by the DOS kernel on INT 25 and INT 26
	supported by PCIBM PC LAN Program, LAN Manage, LANtastic, NetWare, 10NET,
	  etc.
SeeAlso: INT 13/AH=02h,INT 13/AH=03h,INT 25,INT 26,INT 21/AX=5F02h