Fixed compiler warning

include/SDL_stdinc.h

@@ -376,7 +376,7 @@ extern DECLSPEC int SDLCALL SDL_SetMemoryFunctions(SDL_malloc_func malloc_func,
 /**
  *  \brief Get the number of outstanding (unfreed) allocations
  */
-extern DECLSPEC int SDLCALL SDL_GetNumAllocations();
+extern DECLSPEC int SDLCALL SDL_GetNumAllocations(void);
 
 extern DECLSPEC char *SDLCALL SDL_getenv(const char *name);
 extern DECLSPEC int SDLCALL SDL_setenv(const char *name, const char *value, int overwrite);

src/stdlib/SDL_malloc.c

@@ -5312,7 +5312,7 @@ int SDL_SetMemoryFunctions(SDL_malloc_func malloc_func,
     return 0;
 }
 
-int SDL_GetNumAllocations()
+int SDL_GetNumAllocations(void)
 {
     return SDL_AtomicGet(&s_mem.num_allocations);
 }