[Bug libstdc++/81950] New: _GLIBCXX17 macro not used consistently

[Judy.Ward at intel dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81950

            Bug ID: 81950
           Summary: _GLIBCXX17 macro not used consistently
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: Judy.Ward at intel dot com
  Target Milestone: ---

The macro _GLIBCXX17_INLINE is used in most places in the headers to represent
the need for the c++17 inline variable feature. This makes it useful to
compilers (like the Intel compiler) which does not yet have support for this
feature.

However there is one place where this macro is not used - line 366 of utility,
i.e.:
       inline constexpr in_place_t in_place{};

should be:

      _GLIBCXX17 constexpr in_place_t in_place{};

Please fix.

thanks