re PR libstdc++/77727 (Unwrapping std::optional constructor is not working for non-transferable object)

    PR libstdc++/77727
    * include/std/optional (optional(const optional<_Up>&)):
    Default-initialize the base and use emplace.
    (optional(optional<_Up>&&)): Likewise.
    * testsuite/20_util/optional/cons/77727.cc: New.

From-SVN: r240511