Remove obsolete workarounds from placeholders.hpp

include/boost/bind/placeholders.hpp

@@ -10,14 +10,13 @@
 //
 //  bind/placeholders.hpp - _N definitions
 //
-//  Copyright (c) 2002 Peter Dimov and Multi Media Ltd.
-//  Copyright 2015 Peter Dimov
+//  Copyright 2002, 2015, 2024 Peter Dimov
 //
 //  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
 //
-//  See http://www.boost.org/libs/bind/bind.html for documentation.
+//  See http://www.boost.org/libs/bind for documentation.
 //
 
 #include <boost/bind/arg.hpp>
@@ -29,19 +28,7 @@ namespace boost
 namespace placeholders
 {
 
-#if defined(BOOST_BORLANDC) || defined(__GNUC__) && (__GNUC__ < 4)
-
-inline boost::arg<1> _1() { return boost::arg<1>(); }
-inline boost::arg<2> _2() { return boost::arg<2>(); }
-inline boost::arg<3> _3() { return boost::arg<3>(); }
-inline boost::arg<4> _4() { return boost::arg<4>(); }
-inline boost::arg<5> _5() { return boost::arg<5>(); }
-inline boost::arg<6> _6() { return boost::arg<6>(); }
-inline boost::arg<7> _7() { return boost::arg<7>(); }
-inline boost::arg<8> _8() { return boost::arg<8>(); }
-inline boost::arg<9> _9() { return boost::arg<9>(); }
-
-#elif !defined(BOOST_NO_CXX17_INLINE_VARIABLES)
+#if !defined(BOOST_NO_CXX17_INLINE_VARIABLES)
 
 BOOST_INLINE_CONSTEXPR boost::arg<1> _1;
 BOOST_INLINE_CONSTEXPR boost::arg<2> _2;