INT 2F - MDEBUG command driver - INITIALIZE DRIVER                              
	AX = D101h
	CX = command driver counter
Return: DL = status
	    FFh if successful
		CX incremented
	    else error: all registers unchanged
Note:	this function must end with a  far call to the old INT 2F handler after
	  changing the registers
	this function must be reentrant