Fix format string warnings

Also fixes bug #768199:

https://bugzilla.gnome.org/show_bug.cgi?id=768199
diff --git a/timsort.h b/timsort.h
index 795f272..9369e7c 100644
--- a/timsort.h
+++ b/timsort.h
@@ -323,7 +323,7 @@
     SORT_TYPE *tempstore = (SORT_TYPE *)realloc(store->storage, new_size * sizeof(SORT_TYPE));
     if (tempstore == NULL)
     {
-      fprintf(stderr, "Error allocating temporary storage for tim sort: need %lu bytes", sizeof(SORT_TYPE) * new_size);
+      fprintf(stderr, "Error allocating temporary storage for tim sort: need %lu bytes", (unsigned long) (sizeof(SORT_TYPE) * new_size));
       exit(1);
     }
     store->storage = tempstore;