counters. These counters do not exist on all CPUs, but where they
do exist, can be used for counting events such as dcache misses that
would otherwise be difficult or impossible to instrument by code
inspection or hardware simulation.
pmc(9) is meant to be a general interface. Initially, the Intel XScale
counters are the only ones supported.
matching names. This commit might include some private hacks that have been
lurking in my tree a while. They're all harmless, and this reduces the number
of gratuitous diffs I have to deal with.
