Network Accept tracker to handle empty address

If an application calls accept() with the addr argument set to NULL, then the remote IP address and port will be set to 0. The networkTracker::seenAccept() function needs to recognise this situation and look up the details in /proc using the file descriptor. If the connection isn't in /proc then it should return true with both addresses and ports set to 0, so that the received connection is still reported, even though the addresses and ports are empty.

A further enhancement would be to track calls to bind() and store the local address and port against the file descriptor, so that in the condition where addr is NULL, the local port can be used to match against the cache of connections.

Start at networkTracker::seenAccept() and trace how accept() handles a NULL addr argument. Inspect /proc lookup by file descriptor and the existing connection-reporting path; done means connections are still reported with zeroed addresses and ports when no /proc entry exists. The optional bind() tracking is a separate enhancement.