(svn r3155) -Feature: [autoreplace] autoreplace can now remove cars from too long trains

-Trains will now remember the length of stations it visits and sell cars
        when being autoreplaced if they became too long
        -If it needs to remove cars, then it starts from the front and sells
        all it can find until the train is short enough
        -This only works for trains, that knows the station length of the route
        so a full uninterrupted run is needed
        -a train needs 1-2 runs to detect if the shortest station is expanded
        -This feature can be turned on and off in the train replace window
        and each company can have it's own setting
        -NOTE: minor savegame version bump

player.h

@@ -190,6 +190,7 @@ typedef struct Player {
 	PlayerEconomyEntry old_economy[24];
 	EngineID engine_replacement[TOTAL_NUM_ENGINES];
 	bool engine_renew;
+	bool renew_keep_length;
 	int16 engine_renew_months;
 	uint32 engine_renew_money;
 } Player;