Partial, incomplete implementation of new city limits code
BIG structural commit: store "halt" in grund_t, not in plan_t.  Allows for different owners of stations stacked on top of each other (though this feature is not yet implemented).  Also, store 3d "last stop" position in vehicles (necessary as a consquence).  Eliminate resulting dead code.
Bump version to 12 to enable proper save of 3d "last_stop_pos".
Rearrange grund_t data to optimize aligned access
Merge branch 'ncn-devel' into fix-city-limits
Implement more restrictive version of city limits.
Fix small errors in city limits code.
Fix further bugs in city limits code.
Fix display of city limits, which had off-by-one and off-by-one-half errors.
Fix calculation of city limits after city builds bridge & building.
Merge branch 'fix-city-limits' of git://github.com/neroden/simutrans.git into devel-new
VERSION: Step to 12.9000
Merge branch '11.x' into devel-new
Merge branch '11.x' into devel-new
Merge tag 'fix-city-limits-branchpoint' into fix-city-limits
Merge branch 'ncn-devel' into fix-city-limits
Fix problem of disappearing freight correctly.
Merge branch 'ncn-devel' into fix-city-limits
Avoid remarking city tiles repeatedly during loading.  Reset city borders when appropriate.  Fix nasty bug induced by use of the FOR macro, which is defective under optimization.
Remove debugging code inserted during last commit; we appear to have fixed the bug...