Fixed compile warning

src/stdlib/SDL_malloc.c

@@ -2946,13 +2946,17 @@ static void
 internal_malloc_stats(mstate m)
 {
     if (!PREACTION(m)) {
+#ifndef LACKS_STDIO_H
         size_t maxfp = 0;
+#endif
         size_t fp = 0;
         size_t used = 0;
         check_malloc_state(m);
         if (is_initialized(m)) {
             msegmentptr s = &m->seg;
+#ifndef LACKS_STDIO_H
             maxfp = m->max_footprint;
+#endif
             fp = m->footprint;
             used = fp - (m->topsize + TOP_FOOT_SIZE);