trace: add "-trace help"

Print a list of trace points

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-id: 1452174932-28657-7-git-send-email-den@openvz.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

trace/control.h

@@ -181,6 +181,13 @@ void trace_init_events(const char *file);
  */
 void trace_init_file(const char *file);
 
+/**
+ * trace_list_events:
+ *
+ * List all available events.
+ */
+void trace_list_events(void);
+
 /**
  * trace_enable_events:
  * @line_buf: A string with a glob pattern of events to be enabled or,