Fix leaking heuristic dissector names.

I believe we started taking copies of these names for lua purposes, but we need
to free them afterwards. This accounts for about half the leaked blocks (though
only a tiny fraction of the memory) valgrind reported on a recent run.

Change-Id: I74a656716cbf169905476f6c3e2cbcb0bd5ac0bc
Reviewed-on: https://code.wireshark.org/review/1580
Reviewed-by: Evan Huus <eapache@gmail.com>

epan/packet.c

@@ -111,6 +111,7 @@ static GHashTable *heur_dissector_lists = NULL;
 static void
 destroy_heuristic_dissector_entry(gpointer data, gpointer user_data _U_)
 {
+	g_free(((heur_dtbl_entry_t*)data)->list_name);
 	g_slice_free(heur_dtbl_entry_t, data);
 }