xfs: new export ops

xfs: new export ops

This one is a lot more complicated than the previous ones.  XFS already had a
very clever scheme for supporting 64bit inode numbers in filehandles, and I've
reworked this to be some kind of a prototype for the generic 64bit inode
filehandle support.

Signed-off-by: Christoph Hellwig <[email protected]>
Cc: Neil Brown <[email protected]>
Cc: "J. Bruce Fields" <[email protected]>
Cc: David Chinner <[email protected]>
Cc: Timothy Shimmin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>