Hello fdclose

Hi,

After our previous discuss  [1] I prepare fdclosedir(3) function which
was committed by Pawel (cc'ed) in commit r254499.

A while ago I also prepare the fdclose function. Unfortunately, this
new function is a little bit more tricky then previous one. Can I ask
you for a review of this patch?

Thanks,
Mariusz

[1] http://lists.freebsd.org/pipermail/freebsd-arch/2013-August/014688.html