[Bug libstdc++/64467] [5 Regression] 28_regex/traits/char/isctype.cc and wchar_t/isctype.cc

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64467

--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> ---
In the POSIX (i.e. "C") locale it should only be space and tab, but
implementing that when the target only has 8-bits for the ctype mask and
doesn't have a blank class is very difficult.

For other locales it's OK for newline to be in the blank class.