man-pages 3.45, if_nameindex(3): double negation

Hi,

I noticed a double negation in the man page of if_nameindex(3) (present
in 3.45 and online version dating from 2012-12-20):

ERRORS         top

       if_nameindex() may fail and set errno if:

       ENOBUFS
              Insufficient resources unavailable.
              ^^^^^^^^^^^^           ^^^^^^^^^^^

Patch attached replacing unavailable into available.

Cheers,

Cédric