(svn r7473) -Fix (r7269): Pass a cargo type to determine the freight weight
multiplier instead of a vehicle. Fixes incorrect display of total
train capacity.

(svn r6529) -Fix r6513: [depot window] added missing switch in CcCloneVehicle()
The result of this missing switch was asserts in some cloning conditions (not all) (spotted by KUDr)

(svn r6524) -Code cleanup r6515: cleaned up the command to start/stop all vehicles in a depot.
IsWholeTrainInDepot() is removed as CheckTrainInDepot() could be used instead
Cleaned up the check to see if a vehicle is valid for start/stop

(svn r6137) -Codechange: some very minor cleanups:
- Start using DeleteXXX for every pool item, not manually doing it
- Use some wrapper to improve logic
- Rewrote some pieces to improve logic

(svn r3403) -Codechange: [multiheaded engines] the references between the front and rear engines are no longer saved
instead the pointers are generated on load

(svn r3218) -Feature: Multiheaded train engines will now stay in the same train
This means that any user attempt to remove a rear engine will tell the user to move the front engine instead
This fixes the assert when moving multiheaded engines (introduced in r3144)
Note: to make old savegames use this feature, some engines might be turned around in order to link engines in pairs

-Codechange: train subtype is now a bitmask
This allows fast access to info like if it is a wagon or engine and if it is in front and so on
Note: savegame version bump