[Bug libstdc++/81064] [8 Regression] Inline namespace regression

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81064

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Maybe we could take this opportunity to get rid of most of the __8 namespaces
and only have std::__8 and __gnu_cxx::__8, rather than std::__8 and numerous
std::xxx::__8 namespaces.

That would simplify the code, as the correct placement of
__GLIBCXX_BEGIN_NAMESPACE_VERSION and _GLIBCXX_END_NAMESPACE_VERSION is a
constant source of bugs.