(svn r8455) -Codechange: Give a more meaningful name (railveh_type)to member flags of RailVehInfo, as well as changing the code to reflect the fact that it was not a flag but rather a one value only variable. Doing so, some evaluations have been simplified.
-Codechange: Add and use RAILVEH_SINGLEHEAD when railveh_type is set to 0, which was implicit before.
-Cleanup: Remove some extraneous parenthesis.