Revert "externals: Update boost to 1.72 and add Boost Context"

boost/safe_numerics/concept/safe_numeric.hpp

@@ -0,0 +1,34 @@
+#ifndef BOOST_NUMERIC_CONCEPT_SAFE_NUMERIC_HPP
+#define BOOST_NUMERIC_CONCEPT_SAFE_NUMERIC_HPP
+
+//  Copyright (c) 2015 Robert Ramey
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#include <limits>
+#include <typetraits>
+#include <boost/concept/usage.hpp>
+#include "concept/numeric.hpp"
+
+namespace boost {
+namespace safe_numerics {
+
+template<class T>
+struct SafeNumeric : public Numeric<T> {
+    static_assert(
+        is_safe<T>::value,
+        "std::numeric_limits<T> has not been specialized for this type"
+    );
+    BOOST_CONCEPT_USAGE(SafeNumeric){
+        using t1 = get_exception_policy<T>;
+        using t2 = get_promotion_policy<T>;
+        using t3 = base_type<T>;
+    }
+};
+
+} // safe_numerics
+} // boost
+
+#endif // BOOST_NUMERIC_CONCEPT_SAFE_NUMERIC_HPP