[Bug libstdc++/67015] "^[a-z0-9][a-z0-9-]*$", std::regex::extended is miscompiled

[doko at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67015

--- Comment #3 from Matthias Klose <doko at gcc dot gnu.org> ---
patch posted at
https://gcc.gnu.org/ml/gcc-patches/2015-07/msg02177.html
https://gcc.gnu.org/ml/libstdc++/2015-07/msg00068.html