available (closefrom() was added to FreeBSD in 8.0-release).
The selection is made at compile-time, as I still compile a
FreeBSD-based version of lpr&friends on other platforms.
While testing I out that (at least on my system) lpd has been
closing 11095 fd's, when there are only 6 fd's open. The old
code took 120 times more clocktime than calling closefrom().
(although that was still less than 2/1000-ths of a second!)
Reviewed by: jilles
MFC after: 2 weeks
137076c5f7