Include string.h again from memset

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6890 8aca7d54-2c30-db11-9de9-000461428c89
Add errno.h

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6891 8aca7d54-2c30-db11-9de9-000461428c89
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
redraw loading screen and sleep CPU when not needed