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

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

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+/*!
+@file
+Forward declares `boost::hana::fuse`.
+
+@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_FUSE_HPP
+#define BOOST_HANA_FWD_FUSE_HPP
+
+#include <boost/hana/config.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    //! Transform a function taking multiple arguments into a function that
+    //! can be called with a compile-time `Foldable`.
+    //! @ingroup group-Foldable
+    //!
+    //!
+    //! This function is provided for convenience as a different way of
+    //! calling `unpack`. Specifically, `fuse(f)` is a function such that
+    //! @code
+    //!     fuse(f)(foldable) == unpack(foldable, f)
+    //!                       == f(x...)
+    //! @endcode
+    //! where `x...` are the elements in the foldable. This function is
+    //! useful when one wants to create a function that accepts a foldable
+    //! which is not known yet.
+    //!
+    //! @note
+    //! This function is not tag-dispatched; customize `unpack` instead.
+    //!
+    //!
+    //! Example
+    //! -------
+    //! @include example/fuse.cpp
+#ifdef BOOST_HANA_DOXYGEN_INVOKED
+    constexpr auto fuse = [](auto&& f) {
+        return [perfect-capture](auto&& xs) -> decltype(auto) {
+            return unpack(forwarded(xs), forwarded(f));
+        };
+    };
+#else
+    struct fuse_t {
+        template <typename F>
+        constexpr auto operator()(F&& f) const;
+    };
+
+    constexpr fuse_t fuse{};
+#endif
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_FWD_FUSE_HPP