third_party: Add the libsync library from Android

third_party/libsync/include/sync/sync.h

Index: third_party/libsync/include/sync/sync.h
diff --git a/third_party/hwcplus/include/sync/sync.h b/third_party/libsync/include/sync/sync.h
similarity index 89%
copy from third_party/hwcplus/include/sync/sync.h
copy to third_party/libsync/include/sync/sync.h
index 2e5d82f158735814748b2b8015f067732f22631f..461c007e89cbe444d28b6c7ac48a10536828d5fd 100644
--- a/third_party/hwcplus/include/sync/sync.h
+++ b/third_party/libsync/include/sync/sync.h
@@ -16,13 +16,15 @@
  *  limitations under the License.
  */
 
-#ifndef __SYS_CORE_SYNC_H
-#define __SYS_CORE_SYNC_H
+#ifndef _THIRD_PARTY_SYNC_H
+#define _THIRD_PARTY_SYNC_H
 
 #include <sys/cdefs.h>
 #include <stdint.h>
 
-__BEGIN_DECLS
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 // XXX: These structs are copied from the header "linux/sync.h".
 struct sync_fence_info_data {
@@ -49,6 +51,8 @@ struct sync_pt_info *sync_pt_info(struct sync_fence_info_data *info,
                                   struct sync_pt_info *itr);
 void sync_fence_info_free(struct sync_fence_info_data *info);
 
-__END_DECLS
+#ifdef __cplusplus
+}
+#endif
 
-#endif /* __SYS_CORE_SYNC_H */
+#endif /* _THIRD_PARTY_SYNC_H */