Add the MBUF_DEBUG option. This is a fairly invasive option that should

Add the MBUF_DEBUG option.  This is a fairly invasive option that should
not be used on production boxes.  All active mbufs are tracked with a separate
tracking structure and arranged in a RB tree.  A kernel built with this
option can dump all active mbufs with 'sysctl kern.ipc.showmbufs'.

A person debugging the kernel can sprinkle mbuftrackid() calls in the code
to associate an integer id with an mbuf to make the sysctl output more
useful.

The size of the mbuf structure is NOT changed through the use of this option,
but mbuf management overhead will be increased.