9.527 logb

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

Gnulib module: logb

Portability problems fixed by Gnulib:

• This function is missing on some platforms: Minix 3.1.8, MSVC 9.
• This function is missing a declaration on some platforms: Cygwin 1.5.x.
• This function produces wrong results for subnormal numbers on some platforms: glibc 2.11/ppc, glibc 2.7/sparc, glibc 2.7/hppa, Solaris 11 2011-11, Cygwin 1.5.x.

Portability problems not fixed by Gnulib: