[mkgmap-dev] Commit r4392: reafctoring (again): redo most changes in SeaGenerator from r4382

Version mkgmap-r4392 was committed by gerd on Fri, 13 Dec 2019 reafctoring (again): redo most changes in SeaGenerator from r4382 r4382 introduced a stupid bug with --precomp-sea which did not show up when compiling only a few tiles. Global variable precompSeaDir was only initialized when a thread was executed for the first time. So, with 4 threads the first 4 tiles were okay. In my test data those where the ones with sea, bad luck :( Now, this variable is kept in the "ThreadLocal" variables. This allowed to change two more methods to static. http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4392