Add name_set typedef

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/util/name_set.h

@@ -0,0 +1,12 @@
+/*
+Copyright (c) 2013 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Leonardo de Moura
+*/
+#pragma once
+#include <unordered_set>
+#include "name.h"
+namespace lean {
+typedef std::unordered_set<name, name_hash, name_eq> name_set;
+}