5 POSIX specification: @url{http://www.opengroup.org/susv3xsh/isinf.html}
9 Portability problems fixed by Gnulib:
13 Portability problems not fixed by Gnulib:
16 This function is missing on some platforms:
17 AIX 4.3.2, IRIX 6.5, OSF/1 5.1, Solaris 10.