[Bug libstdc++/70722] include_next in cmath skips user-defined wrapper

[guido at trentalancia dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70722

--- Comment #6 from guido at trentalancia dot net ---
Reported as a RESOLVED FIXED bug in firefox:
https://bugzilla.mozilla.org/show_bug.cgi?id=1245076