[Bug c++/79369] namespace definition with qualified id

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79369

--- Comment #1 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
Ah 'namespace X::Y' is permitted to create namespace X.  However the following
is ill-formed, but we accept w/o error:

namespace X {}
inline namespace X {} // ERROR

inline namespace Y {}
namespace Y {} // OK