Add parsed TLV helpers from OsmoBTS

Add functions to copy and merge parsed TLV structures from OsmoBTS.

Change-Id: Ieaaaed19da9c069fe451faa53d24c5b84d7d5615
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 199d05a..b84f859 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -324,6 +324,8 @@
 tvlv_att_def;
 vtvlv_gan_att_def;
 
+osmo_tlvp_copy;
+osmo_tlvp_merge;
 osmo_shift_v_fixed;
 osmo_match_shift_tv_fixed;
 osmo_shift_tlv;