[Bug libstdc++/60401] stdlib.h does not provide abs(long) overload

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60401

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The isnan and isinf errors need a glibc fix, which will be in glibc 2.23, the
rest I have a patch for.