bbd2osm: handle category "RW2?"
show_bbbike_suggest_toplevel and temporary file fixes

* make sure the output file is flushed
* use descriptive temporary filename
show_bbbike_suggest_toplevel: use German sort
show_bbbike_suggest_toplevel: prefer strassen over Berlin.coords.data

This has the following advantages:
* exact coordinates (Berlin.coords.data is partially very approximate)
* works also for osm data created by osm2bbd (no Berlin.coords.data is
  available here, and opensearch.streetnames is usually also missing)
added marathon teaser
data update