(svn r6049) -Codechange: forgot EngineRenew in r6047
-Codechange: cleaned up the EngineRenew code a bit (coding style mostly)
-Codechange: forgot the correct comment in station_cmd
-Codechange: move pool-stuff to engine.h, like we always do

/* $Id */

KNOWN BUGS / PROBLEMS:

Normal and elrail depots look the same. Use 'X' (transparent buildings)
   to distinguish between them
Missing curors / icons for construction (currently using the conventional ones)