Use uint32 instead of SDL_Color

src/common/game_state.h

@@ -1,7 +1,6 @@
 #pragma once
 
 #include <glib-2.0/glib.h>
-#include <SDL3/SDL.h>
 
 #include <common/world.h>
 
@@ -9,7 +8,7 @@ typedef struct Player
 {
   unsigned int id;
   const char *name;
-  SDL_Color color;		/* 4 bytes */
+  guint32 color;		/* 4 bytes */
 
   unsigned int power;
   unsigned int population, max_population;