netbsd-mips64 Buildbot worker

Hello list.

Thank you for the input you have provided so far, it was helpful in
exploring the MIPS aspect of NetBSD. Today I managed to commission the
first version of the "netbsd-mips64" worker for this Buildbot setup:

https://ci.tcpdump.org/#/workers

For the time being netbsd-mips64 is going to run the mips64eb (n32)
build. As soon as the n64 build settles enough, it would be interesting
to switch the worker to it. Meanwhile the n64 port can be run on a
spare Octeon box if required.

Regardless of particular build, this worker is going to be based on some
arbitrarily chosen daily snapshots, so it is going to test NetBSD to an
extent as well. You are welcome to take advantage of it, in that if you
need specific snapshots tested, let me know and I will reinstall the
system. Remote access can be provided on request. If something breaks
in the process, that's OK. It is the purpose of these Octeon boxes to
make software bugs apparent.

I am looking forward to help removing the obstacles to get NetBSD 10.0
run smoothly on this hardware. If anybody is interested in getting SMP
to work on Octeon, that would be especially welcome.

-- 
    Denis Ovsienko