Use :rfc: and :abbr: sphinx roles

Change-Id: I34e0ddbd644944d98a26f9c0c93ad787b4d93679
diff --git a/changelog.rst b/changelog.rst
index e65718a..c6b611a 100644
--- a/changelog.rst
+++ b/changelog.rst
@@ -4,7 +4,7 @@
 Version 0.3
 -----------
 
-- Rewrite TLV syntax specifications using `IETF Augmented BNF (RFC 5234) <https://tools.ietf.org/html/rfc5234>`__
+- Rewrite TLV syntax specifications using IETF Augmented BNF (:rfc:`5234`)
 
 - Require shortest encoding for TLV-TYPE and TLV-LENGTH numbers