perf record: Add support for AUX area sampling

perf record: Add support for AUX area sampling

Add a 'perf record' option '--aux-sample' to request AUX area sampling.
AUX area sampling uses an overwriting buffer much like snapshot mode, so
adjust the AUX buffer mmapping accordingly. To make it easy to queue
samples for decoding, synthesize an ID index.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20191115124225.5247-7-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>