[Bug libstdc++/78326] incorrect c++ usage in experimental/vector and others? _X_max_align is inaccessible

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78326

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Not actually fixed on trunk yet, as I'm having trouble committing. I'll do it
asap.