fix #9455 - tagchecker: allow `lit` on `advertising=billboard`, rephrase the warning as a more generic one

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6503 0c6e7542-c601-0410-84e7-c038aed88b3b
fix #9453 - tagchecker: allow `segregated` for `railway=crossing`

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6504 0c6e7542-c601-0410-84e7-c038aed88b3b