isinf
=====

POSIX specification:
 https://pubs.opengroup.org/onlinepubs/9699919799/functions/isinf.html

Gnulib module: isinf

Portability problems fixed by Gnulib:

  * This macro is missing on some platforms: AIX 5.1, IRIX 6.5, Solaris 11.4.

Portability problems not fixed by Gnulib:

  * This macro returns an unspecified result when given noncanonical values such as unnormalized numbers, pseudo-denormals, pseudo-NaNs, pseudo-Infinities, and pseudo-zeroes.