Work around sparc64 WITNESS kernel failing to load by moving large witness
data structures from bss to be allocated in witness_initialize().

Tested on sparc64, amd64, arm64, i386, octeon. okay miod@

Add a temporary hack to attach only the first thread of every core for
MULTIPROCESSOR kernels. We map 'struct cpuinfo' at the same virtual
address on every processor, but since threads on the same c

Add a temporary hack to attach only the first thread of every core for
MULTIPROCESSOR kernels. We map 'struct cpuinfo' at the same virtual
address on every processor, but since threads on the same core share
an MMU this doesn't quite work. With the hack we are at least able to
use the other core (and any additional processors).

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Enable ssm(4) and remove hacks that worked around the fact that we didn't
have it.

Add cmp(4), a dummy driver to make attaching CMT cpus easier.

Let other people build sparc64 bsd.mp too.