add value_string definitions for RSL message types
diff --git a/include/osmocom/gsm/rsl.h b/include/osmocom/gsm/rsl.h
index 7e46330..2eb045f 100644
--- a/include/osmocom/gsm/rsl.h
+++ b/include/osmocom/gsm/rsl.h
@@ -23,6 +23,7 @@
 
 const char *rsl_err_name(uint8_t err);
 const char *rsl_rlm_cause_name(uint8_t err);
+const char *rsl_msg_name(uint8_t err);
 
 /* Section 3.3.2.3 TS 05.02. I think this looks like a table */
 int rsl_ccch_conf_to_bs_cc_chans(int ccch_conf);