Add separate TCAP decoder that is not linked to MAP

this way we can parse only the TCAP layer into dialogue portion
and component portion, but without actually parsing those.
diff --git a/ebin/osmo_map.app b/ebin/osmo_map.app
index 651e055..c91ee3d 100644
--- a/ebin/osmo_map.app
+++ b/ebin/osmo_map.app
@@ -1,7 +1,7 @@
 {application, osmo_map,
 	[{description, "Osmocom SS7 MAP"},
 	 {vsn, "1"},
-	 {modules, [map, map_codec]},
+	 {modules, [map, map_codec, tcap_asn]},
 	 {registered, []},
 	 {applications, []},
 	 {env, [