MFC r199946:

MFC r199946:

  Add more statistics variables for IPcomp.

  Try to version the struct in a backward compatible way.
  People asked for the versioning of the stats structs in general before.

Note: old netstat binaries, as only consumer, continue to work as they are
      still using kvm but will not display the new stats. [1]

Discussed with:	rwatson [1]

git-svn-id: svn://svn.freebsd.org/base/stable/8@200148 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f