Implement b2 checks for std lib feature macros.

checks/std/cpp_lib_integer_sequence.cpp

@@ -0,0 +1,32 @@
+//  This file was automatically generated on Sun Feb 10 19:54:19 2019
+//  by libs/config/tools/generate.cpp
+//  Copyright John Maddock 2002-4.
+//  Use, modification and distribution are subject to 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/config for the most recent version.//
+//  Revision $Id$
+//
+
+#ifdef __has_include
+#if __has_include(<version>)
+#include <version>
+#endif
+#endif
+
+#include <utility>
+
+#ifndef __cpp_lib_integer_sequence
+#error "Macro << __cpp_lib_integer_sequence is not set"
+#endif
+
+#if __cpp_lib_integer_sequence < 201304
+#error "Macro __cpp_lib_integer_sequence had too low a value"
+#endif
+
+int main( int, char *[] )
+{
+   return 0;
+}
+