Apply patch from #8408.

Fixes #8408.

[SVN r83958]

test/Jamfile.v2

@@ -65,4 +65,5 @@ test-suite config
     ]
     [ compile-fail threads/test_thread_fail1.cpp ]
     [ compile-fail threads/test_thread_fail2.cpp ]
+    [ compile boost_fallthrough_test.cpp : <toolset>clang:<cxxflags>"-std=c++11 -Wimplicit-fallthrough" <warnings-as-errors>on <warnings>all ]
   ;

test/boost_fallthrough_test.cpp

@@ -0,0 +1,20 @@
+//  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) 
+
+#include <boost/config.hpp> 
+
+int test(int n) 
+{ 
+   switch (n) 
+   { 
+   case 0: 
+      n++; 
+      BOOST_FALLTHROUGH; 
+   case 1: 
+      n++; 
+      break; 
+   } 
+   return n; 
+}
+

test/config_info.cpp

@@ -1100,27 +1100,6 @@ void print_boost_macros()
    PRINT_MACRO(BOOST_NO_USING_TEMPLATE);
    PRINT_MACRO(BOOST_NO_VOID_RETURNS);
 
-
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    // END GENERATED BLOCK
 
    PRINT_MACRO(BOOST_INTEL);
@@ -1132,6 +1111,7 @@ void print_boost_macros()
    PRINT_MACRO(BOOST_STATIC_CONSTEXPR);
    PRINT_MACRO(BOOST_NOEXCEPT);
    PRINT_MACRO(BOOST_FORCEINLINE);
+   PRINT_MACRO(BOOST_FALLTHROUGH);
 }
 
 void print_separator()