special functions have names containing dollar signs, and ignoring
them causes gprof to produce incorrect and sometimes bizarre results.
The comment in the original code said that dollar signs were excluded
because they are used in Pascal labels. That's not much of an
issue these days.
underscore. Use it to avoid seeing badsw when profiling the kernel.
Print times more accurately (e.g. usec in %8.0f format instead of
msec in %8.2f format for averages) if hz >= 10000. This should have
no effect now since profhz is only 1024.
