[mkgmap-dev] Commit r4372: - Correct and document handling of internal tag mkgmap:set_unconnected_type so that it works with overlay lines

Version mkgmap-r4372 was committed by gerd on Fri, 15 Nov 2019 - Correct and document handling of internal tag mkgmap:set_unconnected_type so that it works with overlay lines when the road is not removed with mkgmap:set_unconnected_type=none - Add new tag mkgmap:set_semi_connected_type which works similar but matches only when the road has exactly one connection to any other road. Based on semi_con-v3.patch from September 2017 http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4372