[Bug c++/120635] Support something like [[clang::no_specializations]] attribute

[tkaminsk at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120635

--- Comment #4 from Tomasz Kamiński <tkaminsk at gcc dot gnu.org> ---
And allocator_traits from
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2652r2.html