Improved performance in logger

The line of thought behind this merge request is that we are importing a large record set and each record writes several lines to the log file. And writing to a log file is writing to disk and is usually slow.

So my first step here is to minimize the calls to fputs.

Instead of calling fputs 6 times for a log line, it calls it now one time. I am not sure whether this imroves a lot but it might as we are importing a lot of records and if we log during the import it means we are also writing a lot to disk.

I have not tested this MR nor have I done any measurements whether this improves the actual performance.