Cities were not adopting player-built roads... make them do so.  (Bug reintroduced by James.)
Disallow construction of roads without sidewalks adopted by city.  (A more careful city road adoption rule will have to await better-defined city ownership.)
Attempt to get slightly more consistent city road adoption behavior, for now.
Fix nasty logic error which prevented deletion of elevated roads and tunnels.
Merge branch 'fix-city-limits' of git://github.com/neroden/simutrans.git into devel-new
CHANGE: Cities will only adopt/add pavements ("sidewalks") to roads which abut city buildings.