[mkgmap-dev] Commit r4550: refactoring, no functional change

Version mkgmap-r4550 was committed by gerd on Tue, 16 Jun 2020 refactoring, no functional change rename variable fmt to sb cause it's a StringBuilder, not a Formatter http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4550