RSTP code for test/review

Hi,


Attached is a patch that brings in rapid spanning tree (802.1w)
support. I would appreciate any testing or code review. The states will
be printed out at the moment as packets are transfered and the topo is
calculated, these should stop when it becomes stable.

The requirements are:
 (a) it reaches a stable topology, no constant flipflops
 (b) it calculates the correct topology
 (c) no loops are created

It defaults to RSTP mode but will downgrade any port connected to a
legacy STP network so can be tested even if you dont use RSTP in your
network.

The patch only applies to HEAD, no RELENG_6 patch available sorry. The
code implements chapter 17 of 802.1D-2004 if you really want to get your
hands dirty.

Comments welcome.


cheers,
Andrew