fix #9465, see #9400 - tagchecker: handling of `maxspeed:forward/backward` (to be converted to MapCSS after)

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6526 0c6e7542-c601-0410-84e7-c038aed88b3b
Merge branch 'master' into mirror