CODE: MinGW static link standard libraries for makeobj

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6454 8aca7d54-2c30-db11-9de9-000461428c89
CHG: SDL backend USE_HW now runtime option -use_hw. ADD: use of SDL_Rects for more performance. ADD: multithreaded screen update ala GDI

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6455 8aca7d54-2c30-db11-9de9-000461428c89