CHANGE: More realistic way of dealing with the number of private cars on the streets at any one time.
FIX: Were far too many private cars around at any one time.
TODO: Remove artefacts of old system
FIX: Inappropriate removal of stops in some cases from convoys' schedules when access rights were withdrawn
CHANGE: Remove vestiges of old system for accounting for the number of private cars - should improve performance slightly.
FIX: Cornering weights were not properly considered when routing, leading to odd routes in some cases.
FIX: Prevent overflow in calculation of initial journey time. However, journey time is still limited to a maximum of 6,553.5 minutes (or 109 hours and 13.5 minutes).
FIX: For some reason as yet unascertained, convoys would sometimes become stuck when loading.
CHANGE: Allow/mandate greater routing depth to obviate the need for multiple waypoints for ship routes pending assessment as to whether this is viable in performance terms.
FIX: Railways and canals could be built over other players' railways and canals if that player had allowed access.
REVERT: Players can no longer change a schedule whilst a vehicle is loading so as to evade the loading time, thereby giving rise to an exploit.
CHANGE: A convoy whose schedule is changed while it is loading will now wait until it has finished loading before moving off on its new schedule.
CHANGE: Sending a loading convoy to a depot is only completed after the convoy would have finished loading.
Merge branch '11.x' into 12.x