[Bug libstdc++/81381] std::basic_stringbuf only works with DefaultConstructible allocators

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81381

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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   Target Milestone|---                         |8.0