smaller refcounts is RFC 13, not accepted

Per https://github.com/mozilla/rust/wiki/Meeting-weekly-2014-04-29

No new arguments from when original decision was made.

Author: brson

active/0000-smaller-refcounts.md renamed to rejected/0013-smaller-refcounts.md

@@ -1,5 +1,5 @@
 - Start Date: 2014-03-28
-- RFC PR #: 
+- RFC PR #: 23
 - Rust Issue #: 
 
 # Summary