Add support for selecting and processing PERF_RECORD_SWITCH events for
use by Intel PT.  If they are available, they will be used in preference
to sched_switch events.

This enables an unprivileged user to trace multi-threaded or
multi-process workloads with any level of perf_event_paranoid.  However
it depends on kernel support for PERF_RECORD_SWITCH.

Without this patch, tracing a multi-threaded workload will decode
without error but all the data will be attributed to the main thread.

Without this patch, tracing a multi-process workload will result in
decoder errors because the decoder will not know which executable is
executing.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1439458857-30636-3-git-send-email-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>