macos: note additional vfs features

macos: note additional vfs features

currently we have inode numbers which do not change. note it.
additionally, we support large files. note it.

Reviewed-on: http://gerrit.openafs.org/4973
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 4470d849ec731c97dd2fb02dc6cbfe777949b510)

Change-Id: Iee356a8424efe3c79745bf1bf5a1553c988d9d12
Reviewed-on: http://gerrit.openafs.org/4982
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>