[mkgmap-dev] Commit r4598: improve handling of options when creating the overview map (overview-v6.patch by Ticker Berkin)

Version mkgmap-r4598 was committed by gerd on Sun, 24 Jan 2021 improve handling of options when creating the overview map (overview-v6.patch by Ticker Berkin) - apply --order-by-decreasing-area to overview map (increases the overview map a bit) - don't create empty NOD or NET files http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4598