Suggest a fixed name for logging

[bradanlane]

I've gone ahead and changed log.c so the logging file is a fixed name (traffic.log) rather than a log with a time stamp in it. The reason is to leverage logrotate to manage logs.

I'm not suggesting that "traffic.log" is the best name but the use of logrotate is a nice standard solution for Linux systems. I'm not aware of the Windows equivalent for logrotate.

[bradanlane]

FYI: I've coded this and can submit if desired. It now uses "-o" as a command line argument or "LOGNAME" as a conf file entry. Each take a file name as its argument. When a fie name is provided, activity logging will stay with the named file rather than change with the date.

The assumption is this option is used in conjunction with logrotate. When using logrotate, the copytruncate option is used so the open file is not lost.

If the code is pulled, then the documentation will need to be update to reflect the new options and their behavior / usage. (the current limitation on doc is covered by #30)

[wb2osz]

Similar functionality is now in the "dev" branch.
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