Add BOOST_INLINE_CONSTEXPR convenience macro

doc/macro_reference.qbk

@@ -978,6 +978,7 @@ provide compliant C++17 support.
 [table
 [[Macro ][ Description ]]
 [[`BOOST_INLINE_VARIABLE`][This macro expands to `inline` on compilers that support C++17 inline variables and to nothing otherwise. Users may need to check for `BOOST_NO_CXX17_INLINE_VARIABLES` for further adjustments to the code.]]
+[[`BOOST_INLINE_CONSTEXPR`][This is a shortcut for `BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST`.]]
 ]
 
 [endsect]

include/boost/config/detail/suffix.hpp

@@ -1003,6 +1003,8 @@ namespace std{ using ::type_info; }
 #define BOOST_INLINE_VARIABLE
 #endif
 
+#define BOOST_INLINE_CONSTEXPR  BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST
+
 //
 // Unused variable/typedef workarounds:
 //