3be9ded290
LWG 3035. std::allocator's constructors should be constexpr * include/bits/allocator.h (allocator): Add constexpr to constructors for C++2a. Replace dynamic exception specifications with NOTHROW macro. (allocator, operator==, operator!=): Replace USE_NOEXCEPT macro with NOTHROW. * include/bits/c++config (_GLIBCXX20_CONSTEXPR): Define. * include/ext/malloc_allocator.h (malloc_allocator): Add constexpr to constructors for C++2a. * include/ext/new_allocator.h (new_allocator): Likewise. From-SVN: r261703