New file descriptor allocation code in FreeBSD

[Skip Ford]

Xin LI wrote:
> FYI, the performance difference caused by this commit is very impressive on
> FreeBSD:
> 
> http://people.freebsd.org/~des/fdbench/
> 
> While porting this back to -STABLE and DragonFly is not trivial (many 5-ish
> calls :( ), but I think it is worthy to have a look on it :)

I ported the original patch Tim posted.  It's been in my tree for
a while now but I haven't had much of a chance to test it.
Porting it was straight forward so porting DES's version shouldn't
be too difficult.

-- 
Skip