perf machine: Introduce synthesize_threads method out of open coded equivalent

Further simplifications to be done on following patch, as most tools
don't use the callback, using instead just the canned
machine__process_event one.

Cc: Adrian Hunter <adrian.hunter@intel.com>
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: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-r1m0vuuj3cat4bampno9yc8d@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/machine.h

@@ -4,6 +4,7 @@
 #include <sys/types.h>
 #include <linux/rbtree.h>
 #include "map.h"
+#include "event.h"
 
 struct addr_location;
 struct branch_stack;
@@ -178,4 +179,7 @@ int machine__for_each_thread(struct machine *machine,
 			     int (*fn)(struct thread *thread, void *p),
 			     void *priv);
 
+int machine__synthesize_threads(struct machine *machine, struct perf_tool *tool,
+				struct perf_target *target, struct thread_map *threads,
+				perf_event__handler_t process, bool data_mmap);
 #endif /* __PERF_MACHINE_H */