vol: Handle large volume IDs in VLockFile

vol: Handle large volume IDs in VLockFile

VLockVolumeByIdNB currently cannot handle volume IDs larger than
2^31-1. Fix this by using struct flock64, F_SETLKW64, and F_SETLK64 in
the VLockFile functions where possible.

Thanks to Simon Wilkinson for pointing out F_SETLK64.

Change-Id: I422c685aec035716e2f42d13bd97541425ead6a2
Reviewed-on: http://gerrit.openafs.org/4198
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>