third_party: Add the libsync library from Android

third_party/libsync/include/sync/sync.h

 /*
  *  sync.h
  *
  *   Copyright 2012 Google, Inc
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
  *  You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  *  Unless required by applicable law or agreed to in writing, software
  *  distributed under the License is distributed on an "AS IS" BASIS,
  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *  See the License for the specific language governing permissions and
  *  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 {
  uint32_t len;
  char name[32];
  int32_t status;
  uint8_t pt_info[0];
 };
 
 struct sync_pt_info {
  uint32_t len;
  char obj_name[32];
  char driver_name[32];
  int32_t status;
  uint64_t timestamp_ns;
  uint8_t driver_data[0];
 };
 
 /* timeout in msecs */
 int sync_wait(int fd, int timeout);
 int sync_merge(const char *name, int fd1, int fd2);
 struct sync_fence_info_data *sync_fence_info(int fd);
 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 */