stabilize build system: depends, installer, boost/bdb fixes, cross targets groundwork

depends/x86_64-pc-linux-gnu/include/boost/hana/sum.hpp

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+/*!
+@file
+Defines `boost::hana::sum`.
+
+@copyright Louis Dionne 2013-2017
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
+ */
+
+#ifndef BOOST_HANA_SUM_HPP
+#define BOOST_HANA_SUM_HPP
+
+#include <boost/hana/fwd/sum.hpp>
+
+#include <boost/hana/concept/foldable.hpp>
+#include <boost/hana/concept/monoid.hpp>
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/dispatch.hpp>
+#include <boost/hana/fold_left.hpp>
+#include <boost/hana/integral_constant.hpp> // required by fwd decl
+#include <boost/hana/plus.hpp>
+#include <boost/hana/zero.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    template <typename M>
+    struct sum_t {
+    #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
+        static_assert(hana::Monoid<M>::value,
+        "hana::sum<M> requires 'M' to be a Monoid");
+    #endif
+
+        template <typename Xs>
+        constexpr decltype(auto) operator()(Xs&& xs) const {
+            using S = typename hana::tag_of<Xs>::type;
+            using Sum = BOOST_HANA_DISPATCH_IF(sum_impl<S>,
+                hana::Foldable<S>::value
+            );
+
+        #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
+            static_assert(hana::Foldable<S>::value,
+            "hana::sum<M>(xs) requires 'xs' to be Foldable");
+        #endif
+
+            return Sum::template apply<M>(static_cast<Xs&&>(xs));
+        }
+    };
+
+    template <typename T, bool condition>
+    struct sum_impl<T, when<condition>> : default_ {
+        template <typename M, typename Xs>
+        static constexpr decltype(auto) apply(Xs&& xs) {
+            return hana::fold_left(static_cast<Xs&&>(xs), hana::zero<M>(), hana::plus);
+        }
+    };
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_SUM_HPP