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

depends/x86_64-pc-linux-gnu/include/boost/process/exception.hpp

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+// Copyright (c) 2016 Klemens D. Morgenstern
+//
+// 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)
+
+#ifndef BOOST_PROCESS_EXCEPTION_HPP_
+#define BOOST_PROCESS_EXCEPTION_HPP_
+
+#include <system_error>
+
+namespace boost
+{
+namespace process
+{
+///The exception usually thrown by boost.process.
+/** It merely inherits [std::system_error](http://en.cppreference.com/w/cpp/error/system_error)
+ * but can then be distinguished in the catch-block from other system errors.
+ *
+ */
+struct process_error : std::system_error
+{
+    using std::system_error::system_error;
+};
+
+}
+}
+
+
+
+#endif /* BOOST_PROCESS_EXCEPTION_HPP_ */