replaced the windows fixes back into the rebased code

src/common/util.cpp

@@ -115,6 +115,24 @@ static int flock_exnb(int fd)
 
 namespace tools
 {
+
+  void copy_file(const std::string& from, const std::string& to)
+  {
+    using boost::filesystem::path;
+  #if BOOST_VERSION < 107400
+    // Remove this preprocessor if/else when we are bumping the boost version.
+    boost::filesystem::copy_file(
+        path(from),
+        path(to),
+        boost::filesystem::copy_option::overwrite_if_exists);
+  #else
+    boost::filesystem::copy_file(
+        path(from),
+        path(to),
+        boost::filesystem::copy_options::overwrite_existing);
+  #endif
+  }
+
   std::function<void(int)> signal_handler::m_handler;
 
   private_file::private_file() noexcept : m_handle(), m_filename() {}