[Bug libstdc++/68058] _GLIBCXX_BEGIN_NAMESPACE_VERSION breaks regex

[dmorilha at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68058

--- Comment #1 from Daniel Morilha <dmorilha at gmail dot com> ---
Created attachment 36564
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36564&action=edit
regex patch