perf machine: Introduce struct machines

That consolidates the grouping of host + guests, isolating a bit more of
functionality now centered on 'perf_session' that can be used
independently in tools that don't need a 'perf_session' instance, but
needs to have all the thread/map/symbol machinery.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-c700rsiphpmzv8klogojpfut@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-record.c

@@ -571,8 +571,8 @@ static int __cmd_record(struct perf_record *rec, int argc, const char **argv)
 		       "Check /proc/modules permission or run as root.\n");
 
 	if (perf_guest) {
-		machines__process(&session->machines,
-				  perf_event__synthesize_guest_os, tool);
+		machines__process_guests(&session->machines,
+					 perf_event__synthesize_guest_os, tool);
 	}
 
 	if (!opts->target.system_wide)