INT 21 - F-DRIVER.SYS v1.14+ - GRAB INT 21

	AX = 4BEEh
Return: AX = status
	    1234h grab was successful
	    2345h failed (INT 21 grabbed previously)
Program: F-DRIVER.SYS is part of the shareware F-PROT virus/trojan protection
	  package by Fridrik Skulason
Note:	when called the first time, this function moves the INT 21 monitoring
	  code from its original location in the INT 21 chain to be the first
	  thing called by INT 21.  This is the mechanism used by F-NET.
SeeAlso: INT 2F/AX=4653h/CX=0002h,INT 2F/AX=4653h/CX=0007h