[Bug libstdc++/111129] std::regex incorrectly matches quantifiers with plus appended

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111129

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I have a patch to reject "a++" and "a**" but it doesn't work for "a+?" which is
invalid for POSIX REs, but valid for ECMAScript.