[Bug libstdc++/115497] __is_pointer doesn't compile with clang since 014879ea4c86b3b8ab6b61a1226ee5b31e816c8b

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115497

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I suppose we can just include <type_traits> at the top of
<bits/cpp_type_traits.h>, we could even make that conditional on __clang__