New APIs: vfs-label and vfs-uuid return label and uuid for many fs types.

New APIs: vfs-label and vfs-uuid return label and uuid for many fs types.

These APIs generalize the existing 'get-e2label' and 'get-e2uuid'
calls, to provide calls which should be able to get the label
and UUID for most filesystem types.  These use 'blkid' to do the
work.

I have tested that the blkid commands themselves work on RHEL 5.

(Suggested by Yufang Zhang).