Add setting to control whether trains can crash with other companies'.

src/settings_gui.cpp

@@ -1661,6 +1661,7 @@ static SettingsContainer &GetSettingsTree()
 			disasters->Add(new SettingEntry("difficulty.economy"));
 			disasters->Add(new SettingEntry("difficulty.vehicle_breakdowns"));
 			disasters->Add(new SettingEntry("vehicle.plane_crashes"));
+			disasters->Add(new SettingEntry("vehicle.no_train_crash_other_company"));
 		}
 
 		SettingsPage *genworld = main->Add(new SettingsPage(STR_CONFIG_SETTING_GENWORLD));