Windows: add cm_BPlusDirEnumBulkStatOne

Windows: add cm_BPlusDirEnumBulkStatOne

cm_BPlusDirEnumBulkStatOne() is similar to cm_BPlusDirEnumBulkStat()
except that it is used to obtain the status info for one FID in
particular via RXAFS_InlineBulkStat, the parent directory FID, and
up to 48 other FIDs in the same directory which do not currently
have a registered callback.

The parent directory is included to prevent the directory FID
callback from expiring when a directory such as /afs/andrew.cmu.edu/usr/
that requires more status objects then exist in the cache are continuously
recycled.

Up to 48 other FIDs are requested since in most cases on Windows
every entry in a directory is required for an enumeration.

Change-Id: Ic53134498ac0e776232a6f9c97cdb26367959546
Reviewed-on: http://gerrit.openafs.org/5345
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>