* fcntl.cc (_fcntl): Rearrange as wrapper function. Move all

    * fcntl.cc (_fcntl): Rearrange as wrapper function. Move all
        functionality except F_DUPFD to fhandler classes.
        * fhandler.cc (fhandler_base::fcntl): New method.
        * net.cc (fhandler_socket::fcntl): Ditto.
        * fhandler.h (class fhandler_base): Add method prototype for fcntl().
        (class fhandler_socket): Ditto.