abis: add message type names

Add human-readable names for Message Types from 3GPP TS 52.021 ยง9.1

Related: OS#1614

Change-Id: Ide8202b4387351f57ceee34a9eb8c30aef09a663
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index cd4c0ab..5649e71 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -29,6 +29,7 @@
 abis_nm_ipa_magic;
 abis_mm_event_cause_names;
 abis_nm_pcause_type_names;
+abis_nm_msgtype_names;
 abis_nm_att_names;
 
 osmo_sitype_strs;