Added thirdparty: boost library

thirdparty/include/boost/multiprecision/detail/itos.hpp

@@ -0,0 +1,39 @@
+///////////////////////////////////////////////////////////////
+//  Copyright 2019 John Maddock. Distributed under the Boost
+//  Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt
+//
+// We used to use lexical_cast internally for quick conversions from integers 
+// to strings, but that breaks if the global locale is something other than "C".
+// See https://github.com/boostorg/multiprecision/issues/167.
+//
+#ifndef BOOST_MP_DETAIL_ITOS_HPP
+#define BOOST_MP_DETAIL_ITOS_HPP
+
+namespace boost { namespace multiprecision { namespace detail {
+
+   template <class Integer>
+   std::string itos(Integer val)
+   {
+      if (!val)  return "0";
+      std::string result;
+      bool isneg = false;
+      if (val < 0)
+      {
+         val = -val;
+         isneg = true;
+      }
+      while (val)
+      {
+         result.insert(result.begin(), char('0' + (val % 10)));
+         val /= 10;
+      }
+      if (isneg)
+         result.insert(result.begin(), '-');
+      return result;
+   }
+
+
+}}} // namespace boost::multiprecision::detail
+
+#endif