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

[vogt at linux dot vnet.ibm.com]

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

--- Comment #11 from Dominik Vogt <vogt at linux dot vnet.ibm.com> ---
Looks good, the errors are gone now.  Thanks!