INT 14 - MX5 Extended FOSSIL(Fido/Opus/Seadog Standard Interface Layer)  A standardized API for performing serial I/O, originally used by the Fido and Opus bulletin- board software and Seadog bulletin-board mailer, but now in wider use. - GET/SET MNP LEVEL
	AX = E001h
	BH = function
	    00h get MNP level
	    01h set MNP level
		BL = new level (00h none, 02h/04h/05h MNP level N)
	DX = port number (0-3)
Return: BL = MNP level
SeeAlso: AX=E002h,AX=E003h,AX=E004h,AX=E006h