[Bug libstdc++/94749] std::istream::ignore discards too many characters

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94749

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The fix is actually not right, it fails to discard the delimiter if it occurs
after ignoring more than numeric_limits<streamsize>::max() characters.

I have a fix for that though.