r3798: added support for alternate data streams in xattrs into pvfs.

r3798: added support for alternate data streams in xattrs into pvfs.

The trickiest part about this was getting the sharing and locking
rules right, as alternate streams are separate locking spaces from the
main file for the purposes of byte range locking, and separate for
most share violation rules.

I suspect there are still problems with delete on close with alternate
data streams. I'll look at that next.