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

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

@@ -0,0 +1,58 @@
+/*!
+@file
+Forward declares `boost::hana::take_back`.
+
+@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_FWD_TAKE_BACK_HPP
+#define BOOST_HANA_FWD_TAKE_BACK_HPP
+
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/when.hpp>
+
+#include <cstddef>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    //! Returns the last `n` elements of a sequence, or the whole sequence
+    //! if the sequence has less than `n` elements.
+    //! @ingroup group-Sequence
+    //!
+    //! Given a `Sequence` `xs` and an `IntegralConstant` `n`, `take_back(xs, n)`
+    //! is a new sequence containing the last `n` elements of `xs`, in the
+    //! same order. If `length(xs) <= n`, the whole sequence is returned and
+    //! no error is triggered.
+    //!
+    //!
+    //! @param xs
+    //! The sequence to take the elements from.
+    //!
+    //! @param n
+    //! A non-negative `IntegralConstant` representing the number of elements
+    //! to keep in the resulting sequence.
+    //!
+    //!
+    //! Example
+    //! -------
+    //! @include example/take_back.cpp
+#ifdef BOOST_HANA_DOXYGEN_INVOKED
+    constexpr auto take_back = [](auto&& xs, auto const& n) {
+        return tag-dispatched;
+    };
+#else
+    template <typename S, typename = void>
+    struct take_back_impl : take_back_impl<S, when<true>> { };
+
+    struct take_back_t {
+        template <typename Xs, typename N>
+        constexpr auto operator()(Xs&& xs, N const& n) const;
+    };
+
+    constexpr take_back_t take_back{};
+#endif
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_FWD_TAKE_BACK_HPP