perf auxtrace: Add option to synthesize branch stacks on samples

Add AUX area tracing option 'l' to synthesize branch stacks on samples
just like sample type PERF_SAMPLE_BRANCH_STACK.  This is taken into use
by Intel PT in a subsequent patch.

Based-on-patch-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1443186956-18718-9-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
index bf72b77..b86f90db 100644
--- a/tools/perf/util/auxtrace.h
+++ b/tools/perf/util/auxtrace.h
@@ -63,7 +63,9 @@
  * @calls: limit branch samples to calls (can be combined with @returns)
  * @returns: limit branch samples to returns (can be combined with @calls)
  * @callchain: add callchain to 'instructions' events
+ * @last_branch: add branch context to 'instruction' events
  * @callchain_sz: maximum callchain size
+ * @last_branch_sz: branch context size
  * @period: 'instructions' events period
  * @period_type: 'instructions' events period type
  */
@@ -79,7 +81,9 @@
 	bool			calls;
 	bool			returns;
 	bool			callchain;
+	bool			last_branch;
 	unsigned int		callchain_sz;
+	unsigned int		last_branch_sz;
 	unsigned long long	period;
 	enum itrace_period_type	period_type;
 };