1G eth UDP / IP Stack

I haven't tested this yet, but reviewing the code in IPv4_RX.vhd, when in state IP_HDR, if rx_count is at the point of checking the DEST_IP_ADDR (ie, between the count of x"0010" and x"0013"), if the ip_addr byte is = x"FF" in any of these, but otherwise matches at least one byte of "our_ip_address", then the packet will be accepted erroneously (again I haven't verified this, this is just by review).

There appears to be code below in this state which was commented out by someone that when rx_count = x"0013" it verified a full match on the dest_ip_address to be either matching our_ip_address or broadcast. It seems to be more correct than whats there now.