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

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

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+/*!
+@file
+Defines `boost::hana::prefix`.
+
+@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_PREFIX_HPP
+#define BOOST_HANA_PREFIX_HPP
+
+#include <boost/hana/fwd/prefix.hpp>
+
+#include <boost/hana/append.hpp>
+#include <boost/hana/chain.hpp>
+#include <boost/hana/concept/monad_plus.hpp>
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/dispatch.hpp>
+#include <boost/hana/functional/partial.hpp>
+#include <boost/hana/lift.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    //! @cond
+    template <typename Xs, typename Pref>
+    constexpr auto prefix_t::operator()(Xs&& xs, Pref&& pref) const {
+        using M = typename hana::tag_of<Xs>::type;
+        using Prefix = BOOST_HANA_DISPATCH_IF(prefix_impl<M>,
+            hana::MonadPlus<M>::value
+        );
+
+    #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
+        static_assert(hana::MonadPlus<M>::value,
+        "hana::prefix(xs, pref) requires 'xs' to be a MonadPlus");
+    #endif
+
+        return Prefix::apply(static_cast<Xs&&>(xs), static_cast<Pref&&>(pref));
+    }
+    //! @endcond
+
+    template <typename M, bool condition>
+    struct prefix_impl<M, when<condition>> : default_ {
+        template <typename Xs, typename Z>
+        static constexpr decltype(auto) apply(Xs&& xs, Z&& z) {
+            return hana::chain(static_cast<Xs&&>(xs),
+                hana::partial(hana::append, hana::lift<M>(static_cast<Z&&>(z))));
+        }
+    };
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_PREFIX_HPP