(svn r3143) -Codechange: greatly increased speed when allocating vehicles
This increases the speed greatly when allocating more than one at a time
(planes, artic engines, cloning...) and when adding another block of
vehicles to the vehicle pool (adding 512 vehicles each time)

(svn r3142) Remove a now invalid case fall-through and use helper function instead of map access.

(svn r3141) Replace incorrect railtype bitmask in CmdRailTrackHelper with appropriate GB()

(svn r3140) Building/removing a waypoint could leave old PBS reservations behind. This ensures they are cleared.

(svn r3139) -NewGRF, Feature: support for articulated rail vehicles. This is used, for example, by coal tenders.

(svn r3138) -Fix: [clone vehicles] fixed assert when it was possible to allocate some vehicles to clone a train, but not for all cars
Now it gives "too many vehicles" error message instead
To make this work, AllocateVehicles() needed to be moved to vehicle.c (from aircraft_cmd.c) and made non-static

(svn r3137) -Fix: [autoreplace] fixed assert that was triggerable when a vehicle entered a depot even though the goto depot was canceled
this assert could be reached by clicking on the goto depot button to cancel goto depot from the orders and the vehicle
still entered the depot. The flags in that case would not be "normal" anymore. An additional check is added to prevent this

(svn r3136) -Fix: [autoreplace] all cargo in engines that consists of more than one vehicle will try to move cargo from all vehicles
currently this applies to planes and multiheaded train engines (no more lost airmail)
added GetNextEnginePart() that returns the next vehicle in an engine nomatter what type it is
when more types of multivehicle engines are added, they will have to be added here too or autoreplace will not remove all cargo

(svn r3135) Use symbolic names in the tables, which hold the information about accepted goods of industry tiles, instead of magic numbers

(svn r3134) Forgot to commit one file in r3133