add 'show mbuf' to ddb in stable/9

[Sebastian Kuzminsky]

Hi folks, I have a very minor patch i'd like to contribute, but i'm not sure what the preferred way to contribute patches is.

The patch adds a command to ddb called "show mbuf", that decodes some of the mbuf info.  We've found it useful for debugging some of the networking code we work on.

The patch is against stable/9.  It is available here:

https://github.com/Seb-LineRate/freebsd/commit/f70f2e0024ecebff6769d7440b8379f3d907457d

I can prepare the patch in other ways if that is preferred, just let me know!


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Sebastian Kuzminsky