LU-9727 lustre: Add an additional set of 64 changelog flags.

LU-9727 lustre: Add an additional set of 64 changelog flags.

This adds a new changelog extension containing 64 additional flag
bits, to be used for future changelog extensions.
The presence of the extension is signalled using the last remaining
unused changelog flag bit.
The new extension is present in all changelog records by default, but
will be removed from records read by legacy changelog consumers.

Signed-off-by: Matthew Sanderson <matthew.sanderson@anu.edu.au>
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Iad05880e82400d7e84d927e84e44d1454e240a80
Reviewed-on: https://review.whamcloud.com/28045
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>