try to move the file from the source to the destination (spool) directory.
If that succeeds, much time and disk-space will be saved by doing that
instead of copying the entire file only to remove the original. This
could be a big win on machines doing samba-service or CAP-based printing.
Note that this is about the fourth or fifth iteration of the patch, after
trying to address all possible security implications of the change.
PR: 16124
Reviewed by: freebsd-current or freebsd-hackers (some time ago)
4c4f66db72