new statx() like interface for libcephfs

[Jeff Layton]

I have a patchset queued up for ceph that adds btime (birthtime)
support to it. What was lacking though was a mechanism to get the btime
out of the inode.

Rather than cook up a brand new interface just for the btime, I decided
to "borrow" the work that David Howells did with the new proposed
statx() interface. The pull request to add this to ceph is up here:

     https://github.com/ceph/ceph/pull/9965

Sage has already closed it out which I take to mean that he has pulled
the patches into a staging branch for eventual merge.

It occurs to me though that I didn't ask anyone who is working on the
samba vfs or ganesha fsal code whether they think this interface is
acceptable.

Since Samba and Ganesha are the targeted users of this interface, it'd
be good to have developers from both communities take a look and see if
there are any problems here.

Does anyone see any issues with the above pull request?
-- 
Jeff Layton <jlayton at redhat.com>