MacOS 10.6 support update

MacOS 10.6 support update

Make things build on MacOS 10.6 again. Don't break 10.5 build.
Fix an error in the MacOS port which was left from previous head.

Reviewed-on: http://gerrit.openafs.org/96
Verified-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Russ Allbery <rra@stanford.edu>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 1d1ae6195bd03c4348a57914cf892e06b507d855)
Reviewed-on: http://gerrit.openafs.org/355
Tested-by: Derrick Brashear <shadow@dementia.org>