Merge branch 'rs/realloc-array'

Code cleanup.

* rs/realloc-array:
  use REALLOC_ARRAY for changing the allocation size of arrays
  add macro REALLOC_ARRAY

fast-import.c

@@ -878,7 +878,7 @@ static void start_packfile(void)
 	pack_size = sizeof(hdr);
 	object_count = 0;
 
-	all_packs = xrealloc(all_packs, sizeof(*all_packs) * (pack_id + 1));
+	REALLOC_ARRAY(all_packs, pack_id + 1);
 	all_packs[pack_id] = p;
 }