gtp: Support tx/rx RAN Information Relay message

See 3GPP TS 29.060 sec 7.5.14.1 RAN Information Relay.

Related: SYS#5314
Change-Id: Iea3eb032ccd4aed5187baca7f7719349d76039d4
diff --git a/TODO-RELEASE b/TODO-RELEASE
index d0852fc..23c9b6d 100644
--- a/TODO-RELEASE
+++ b/TODO-RELEASE
@@ -7,3 +7,4 @@
 # If any interfaces have been added since the last public release: c:r:a + 1.
 # If any interfaces have been removed or changed since the last public release: c:r:0.
 #library	what		description / commit summary line
+libgtp          ADD             gtp_ran_info_relay_req, gtp_set_cb_ran_info_relay_ind