8.129 copysign

POSIX specification:
http://www.opengroup.org/onlinepubs/9699919799/functions/copysign.html

Gnulib module: copysign

Portability problems fixed by Gnulib:

• This function is missing on some platforms: Minix 3.1.8, MSVC 9.

Portability problems not fixed by Gnulib: