An attempt at looking at the sizes of xfs structures with exclusions

An attempt at looking at the sizes of xfs structures with exclusions
for ones that we know are different.
The aim is to help pick up on extensions to structures and addition
of structures which for instance may vary on 32 bit and 64 bit word size
versions.
Merge of master-melb:xfs-cmds:26056a by kenmcd.

  An attempt at looking at the sizes of xfs structures with exclusions
  for ones that we know are different.
  The aim is to help pick up on extensions to structures and addition
  of structures which for instance may vary on 32 bit and 64 bit word size
  versions.