_N placeholders moved to a separate header.

[SVN r12573]

include/boost/bind/arg.hpp

@@ -0,0 +1,30 @@
+#ifndef BOOST_BIND_ARG_HPP_INCLUDED
+#define BOOST_BIND_ARG_HPP_INCLUDED
+
+#if _MSC_VER >= 1020
+#pragma once
+#endif
+
+//
+//  bind/arg.hpp
+//
+//  Copyright (c) 2002 Peter Dimov and Multi Media Ltd.
+//
+//  Permission to copy, use, modify, sell and distribute this software
+//  is granted provided this copyright notice appears in all copies.
+//  This software is provided "as is" without express or implied
+//  warranty, and with no claim as to its suitability for any purpose.
+//
+//  See http://www.boost.org/libs/bind/bind.html for documentation.
+//
+
+namespace boost
+{
+
+template<int I> class arg
+{
+};
+
+} // namespace boost
+
+#endif // #ifndef BOOST_BIND_ARG_HPP_INCLUDED