N3DS: Fix -Wformat warnings in tests.

All warnings were about invalid specifiers. Since U/Sint32 is a long,
using `%d` emits a -Wformat warning.

test/testtimer.c

@@ -33,7 +33,7 @@ ticktock(Uint32 interval, void *param)
 static Uint32 SDLCALL
 callback(Uint32 interval, void *param)
 {
-    SDL_Log("Timer %d : param = %d\n", interval, (int) (uintptr_t) param);
+    SDL_Log("Timer %" SDL_PRIu32 " : param = %d\n", interval, (int) (uintptr_t) param);
     return interval;
 }