fixed compile error with older versions of SDL

src/playturn.cpp

@@ -108,7 +108,7 @@ void play_turn(game_data& gameinfo, game_state& state_of_game,
 		const int res = move_unit(&gui,map,units,teams,route.steps,
 		                          &recorder,&turn_data.undos());
 
-		if(res == route.steps.size())
+		if(size_t(res) == route.steps.size())
 			ui->second.done_goto();
 	}
 

src/sdl_utils.hpp

@@ -22,6 +22,17 @@
 #include <iostream>
 #include <string>
 
+//older versions of SDL don't define the
+//mouse wheel macros, so define them ourselves
+//if necessary.
+#ifndef SDL_BUTTON_WHEELUP
+#define SDL_BUTTON_WHEELUP 4
+#endif
+
+#ifndef SDL_BUTTON_WHEELDOWN
+#define SDL_BUTTON_WHEELDOWN 5
+#endif
+
 struct free_sdl_surface {
 	void operator()(SDL_Surface* surface) const { SDL_FreeSurface(surface); }
 };

src/widgets/menu.cpp

@@ -1,6 +1,7 @@
 #include "menu.hpp"
 
 #include "../font.hpp"
+#include "../sdl_utils.hpp"
 #include "../show_dialog.hpp"
 #include "../video.hpp"