The CAM_DEBUG* macros use multiple printfs to dump the data. This is
suboptimal when tracing things that produce even a moderate amount since
it gets intertwingled. I can't even turn on tracing with a 24-disk HBA
on boot without it getting messed up. Add helper routines to work around
clang's over-use of the stack: that way we only pay the stack penalty
when a trace hits.
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