[make_array] Update documentation.

Point to proposal for C++17 make_array(), and point out the differences of our
implementation.

dune/common/array.hh

@@ -40,7 +40,15 @@ namespace Dune
 
   //! Create and initialize an array
   /**
-   * \note This method is Dune-specific and not part of any C++-standard.
+   * \note This method is a somewhat limited dune-specific version of
+   *       make_array() as proposed for C++17 (see <a
+   *       href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4391.html">N4391</a>,
+   *       accepted <a
+   *       href="https://botondballo.wordpress.com/2015/06/05/trip-report-c-standards-meeting-in-lenexa-may-2015/">May
+   *       2015</a>).  The differeces are that this version should never be
+   *       used with expliclitly given template arguments, or with
+   *       std::reference_wrapper<...> arguments, and we do not give a
+   *       diagnostic when anyone happens to do that.
    */
   template < typename... Args >
   std::array<typename std::common_type<Args...>::type, sizeof...(Args)> make_array(const Args&... args)