(svn r1479) -Added highscore chart (accessible from the difficulty window) with top5 companies for a given difficulty (select the difficulty in the menu)

-Added endgame score on 1 jan 2051 where you are added to the highscore if sufficiently large points have been accumulated. Game is paused while
-These values are saved in hs.dat; added read/write functions for it
-Added code to delete all windows to show charts. There is one issue left: somehow a news-gui pops up in front of the the chart at the end of the game.

table/sprites.h

@@ -722,6 +722,10 @@ enum Sprites {
 	SPR_OTTD_Y                = 4843,
 	SPR_OTTD_C                = 4844,
 
+	SPR_HIGHSCORE_CHART_BEGIN = 4804,
+	SPR_TYCOON_IMG1_BEGIN     = 4814,
+	SPR_TYCOON_IMG2_BEGIN     = 4824,
+
 	/* road_gui.c */
 	SPR_IMG_ROAD_NW				= 1309,
 	SPR_IMG_ROAD_NE				= 1310,