(svn r17818) -Codechange: iterate the cargo list from the back when trying to merge packets. Chances are higher that the last packet (in the FIFO-ish queue) is mergeable with the to be added package. If a train gets loaded packets get split up and put into the different carriages, at unload they are unloaded in the same order so the last in the FIFO-ish queue is likely the packet it can merge with.
This results in a 5-10% performance improvement of CargoList's Append/MoveTo without performance degradation of AgeCargo.