INT 7A - Novell NetWare - SPX Driver - LISTEN FOR SPX CONNECTION

	BX = 0012h
	AH = watchdog flag (00h disabled, 01h enabled)
	AL = retry count (00h = default)
	ES:SI -> Event Control Block (see #03810 at BX=0003h)
Return: nothing
Notes:	there should always be at least two SPX ECB's listening to a socket, so
	  that NetWare can perform its internal packet exchanges
	this function is supported by Advanced NetWare 2.1+
SeeAlso: BX=0011h,BX=0013h,BX=0014h