(svn r5926) -Codechange: make _cur_year contain the full year, instead of the offset since 1920
-Codechange: store all year related variables that are _not_ stored in a savegame/transported over the network in the same format as _cur_year

/* $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)