perf auxtrace: Add support for dumping AUX area samples

Add support for dumping AUX area samples i.e. via the perf script/report
 -D (--dump-raw-trace) option.

Committer notes:

Add __maybe_unused to the two args for auxtrace__dump_auxtrace_sample()
for when we don't HAVE_AUXTRACE_SUPPORT.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20191115124225.5247-10-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>