optopt
======

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

Gnulib module: ---

Portability problems fixed by Gnulib:

Portability problems not fixed by Gnulib:

  * This variable is missing on some platforms: Mac OS X 10.5, IRIX 6.5, OSF/1 5.1, MSVC 9.