(svn r8300) -Codechange: Add a prototype for DrawPlayerIcon to players.h and include that

instead of using externs. Also move DrawPlayerIcon from graph_gui.cpp to
players.cpp.

src/town_gui.cpp

@@ -30,7 +30,6 @@ static const Widget _town_authority_widgets[] = {
 };
 
 extern const byte _town_action_costs[8];
-extern void DrawPlayerIcon(PlayerID pid, int x, int y);
 
 /** Get a list of available actions to do at a town.
  * @param *nump if not NULL add put the number of available actions in it